Recovery and reusability of catalysts is an important aspect in modern catalysis research especially in organic synthesis. Compared to the conventional separation, magnetic separation has emerged as a robust, highly efficient, easy and rapid separation technique for products and catalysts. Cobalt ferrite nanoparticles are a well-known material, recognized as CoFe2O4 MNPs, and can be used as both catalyst and a versatile support for functionalization of metals, organocatalysts. In recent times, catalysis research has clearly experienced a renaissance in the area of utility of cobalt ferrite (CoFe2O4 MNPs) nanocatalysts based on their ability for recovery and reusability; the activity of these CoFe2O4 MNPs was investigated in a category of organic reactions. In this review, the fabrication, characterization, and application of cobalt ferrite (CoFe2O4 MNPs) nanocatalysts (CF-MNPs) in organic reactions have well summarized.
Catalysis plays an increasingly crucial role in chemical processes, and it is widely used at the heart of innumerable chemical processes from scientific research in academic laboratories to an economical research in industrial laboratories . The catalyst is very important in chemistry science especially in organic synthesis; it can greatly promote the chemical processes and reactions and effectively and sustainably synthesize products . The development of new, sustainable chemical processes for the synthesis of natural products, drugs, and biologically active molecules is impossible without the use of catalysis. A catalyst ensures that a specific chemical reaction requires less energy (such as heat). In recent times, catalysts and catalytic reactions have attracted special attention with the aim of finding meaningful applications in the pharmaceutical and fine chemical industries . Catalysis has possessed a key role in improving and developing organic synthesis especially in medical chemistry and has become one of the most economically and ecologically impacting technologies so far . The modern era of organic synthesis is shifting towards the path of creative strategies which fundamentally underlines or focuses on the concept of green chemistry especially the use of sustainable and green catalysts .
1.2 Green and sustainable catalysis
The development of green, sustainable, and economical chemical processes is one of the major challenges in modern chemistry science especially in green chemistry . Green chemistry, also called sustainable chemistry, is a philosophy of chemical research and engineering that encourages the design of products and processes that minimize the use and generation of hazardous substances , . Green catalysis is a subchapter of green chemistry but probably the most important one , and one of the urgently indispensable challenges facing chemists now is the design and use of environmentally benign catalysts . The concept of green chemistry, which makes catalysis science even more creative, has become an integral part of sustainability . From the perspective of green chemistry, an ideal and sustainable catalyst must possess a series of distinctive advantages such as low preparation cost, high activity, efficiency and selectivity, high stability, efficient recovery, and good recyclability . Accordingly, the search for designing and using environmentally benign, sustainable, and efficiently reusable alternative catalytic systems has become an important challenge in modern catalysis science .
1.3 Homogeneous, heterogeneous, and heterogenized catalysis
Catalysts can be divided into two types depending on the reaction phase that they occupy: homogeneous and heterogeneous. Homogeneous catalysis is a type of catalysis in which the catalyst operates in the same phase as the reactants, generally dissolved in the reaction medium; chemists are unanimous on this theory. In homogenous catalytic system, all catalytic sites are accessible because of its solubility in the reaction medium ; it is possible to tune the chemo-, region- and enantioselectivity of the catalyst . Homogeneous catalysts have a series of other advantages such as high selectivities, better yield, high turnover numbers, and easy optimization of catalytic systems by modification of ligand and metals , , , . But here a notable disadvantage is glaring; separating homogenous catalysts from the desired products or reaction medium is a difficult, tedious, and time-consuming task and needs a series of costly and specific techniques . It is essential to remove the catalyst because metal contamination is highly regulated, especially in the drug and pharmaceutical industry . Also, it is not compatible with the principles of green chemistry in modern catalysis science especially from an economic standpoint . To address the separation problems in homogeneous catalysis, chemists focused on designing new, green, and effective heterogonous catalytic systems. Heterogeneous catalysis is a type of catalysis in which the catalyst is present in a different or separate phase; normally the catalyst is a solid and the reactants are gas or liquid. In recent times, heterogenization of active molecules on support materials (such as inorganic silica and organic polymers) has been introduced as an efficient strategy for the developing ecofriendly catalytic systems that facilitate the recovery and reusability of the catalysts , . However, the activities and selectivities of heterogeneous catalysts are generally lower than those of their homogeneous counterparts, due to the lower dimensionality of the interaction between the components and the catalyst surface , . This becomes the crucial factor that restricts it from developing well . In this respect, organic chemists are looking for new heterogeneous catalysts that possess the advantages of both homogenous catalysts (high activity and selectivity, etc.) and heterogeneous catalysts (easy catalyst separation, long catalytic life, thermal stability, and recyclability) .
1.4 Nanocatalysis and magnetic nanoparticles
Nanotechnology is the science and technology of precisely manipulating the structure of matter at the molecular level, in particular things that are <100 nm in size. Nanotechnology is the key and valuable achievement of the 21st century in all sciences, especially in chemistry science. During the last decade, chemistry science has witnessed the birth of a new technology revolution and created huge developments in catalysis as “nanocatalysis”. Nanocatalysis is a hot research topic which involves the use of nanomaterials (an average size of 1–100 nm) as catalysts for a variety of catalysis applications . In fact, the nanocatalysts open up a new and marvelous chapter in catalysis processes and create numerous opportunities for chemists in order to achieve their goals. Nanocatalysts are attractive alternatives to conventional catalysts, because when the size of the material (catalyst or support) is decreased to the nanometer scale, the surface area is significantly increased and the material (catalyst or support) can be equally dispersed in solution, to form a homogenous emulsion . Significant increase in catalytic activity, selectivity, and stability of nanocatalysts can be manipulated by tailoring chemical and physical properties such as size, shape, composition, and morphology . Accordingly, the particle size and support employed for the dispersion of catalyst are two key factors that affect the efficiency of nanocatalysis processes . Nanocatalysts are separated and recovered through filtration or centrifugation strategies. However, in most cases, isolation and recovery of nanocatalysts from the reaction medium is either a very difficult, tedious, and time-consuming task or impossible because their size decreases to nanoscale dimensions .
To overcome such limitations, magnetic separation was introduced as a logical solution , . In recent times, magnetic separation has received profound attention because magnetic nanocatalysts (due to their insoluble and paramagnetic nature) can be readily separated from the reaction medium by using an external magnet, without the need for filtration, centrifugation, or other tedious workup processes , , , , , . Also, most magnetic nanocatalysts (magnetic nanoparticles as catalyst or support) can be reused many times while keeping their initial activity . Furthermore, recent literature studies clearly have shown that magnetic nanoparticles (MNPs) possess several admirable advantages such as high surface area to bulk ratios, low toxicity, high activity, thermal stability, and the capability of surface modifications and easy dispersion , , , , . These characteristics thus make them more sustainable and ideal catalysts or supports than conventional samples . In fact, magnetic separable catalysts are a well-favored and fascinating strategy to bridge the split between heterogeneous and homogenous catalysis , . In describing the MNPs, it can be also said that the magnetic separation is in fact an admirable and valuable victory in areas of catalysis science .
1.5 Cobalt ferrite nanoparticles
Spinel ferrites are also named as cubic ferrites; they are generally applied at microwave frequencies due to high electrical resistivity and low eddy current losses. The chemical formula of spinel ferrites is MFe2O4. In the early 21st century, the spinel ferrite nanoparticles (MFe2O4, in which M represents one or more bivalent transition metals such as Mn, Fe, Co, Ni, Cu, and Zn) have become an important and efficient tool in modern catalytic organic synthesis due to their unique electronic and magnetic properties (easily separate by external magnet), which are quite different from the conventional bulk materials , , , , .
In this category (spinel ferrites), cobalt spinel ferrite (CoFe2O4) is an inverse spinel ferrite with all or most Co+2 ions occupying octahedral sites (B sites) and the Fe+3 ions on both tetrahedral (A sites) and B sites , . Cobalt spinal ferrites (CoFe2O4) have received profound attention due to their strong anisotropy, high coercivity, moderate saturation magnetization, and good mechanical and excellent chemical stabilities at higher temperature, which are significantly different from their bulk counterparts , , . Owing to these features, cobalt ferrites have been widely used in sensors, recording devices, magnetic cards, solar cells, magnetic drug delivery, biomedical, catalysis, and biotechnology , , , . For catalysis applications, CoFe2O4 nanoparticles are required to have a narrow size distribution and high magnetization values . The saturation magnetization (Ms) of CoFe2O4 nanoparticles is less than that of the bulk, and Ms decreases with decrease in size. When the crystallite size is almost equal to single-domain size, the coercivity reaches its highest value.
Compared to CoFe2O4, Fe3O4 and γ-Fe2O3 are more popular and easily prepared and have been efficiently utilized in many organic reactions, but they have a series of drawbacks. For example, Fe3O4 is fairly reactive to acidic and oxidative environments, and γ-Fe2O3 is also not thermally stable . On the contrary, CoFe2O4 nanoparticles have a remarkable chemical stability . The features of CoFe2O4 nanoparticles are strongly dependent on a series of factors such as chemical composition and microstructural characteristics, where the particle size and shape might be controlled in the fabrication processes , . Accordingly, fabrication of ferrite nanoparticles of controllable morphology with excellent magnetic performance is attracting intensive interest .
1.6 Preparation of CoFe2O4 nanoparticles
A number of preparation techniques have been explored to synthesize CoFe2O4 nanoparticles such as microemulsion , sol-gel techniques , hydrothermal synthesis , solvothermal method , co-precipitation , electrochemical method , and combustion methods [52–54]. Although in most of methods, cobalt ferrite nanoparticles are achieved in the desired or required sizes and microstructures, they are difficult to apply on larger scales due to their expensive and complicated procedures, high reaction temperatures, long reaction times, toxic reagents and by-products, and their potential harm to the environment . Among these, co-precipitation and hydrothermal techniques are easy, versatile, and low-cost methods for the preparation of cobalt ferrite nanoparticles. Co-precipitation is a rapid, easy, and economical process that offers a series of advantages such as controlled crystallite size, high limpidness, no agglomeration of the particles, and stable particle surface along with homogeneity . In hydrothermal processes, two factors are very important: (1) optimization of hydrothermal synthetic method and (2) the ion doping or surface modification of cobalt ferrite nanoparticles . Ion doping can lead to structural disorder, change in grain size and lattice strain, and cation redistribution as well as affect the physical and chemical features of cobalt ferrite nanoparticles .
1.7 Modifications of CoFe2O4 nanoparticles
Spinal ferrites nanoparticles, in particular cobalt ferrites, are very sensitive to agglomeration because of their small inter-particle distances and high surface energy and also exhibit high chemical reactivity as well as strong magnetic dipole interactions . Natural agglomeration of these particles into larger clusters also restricts the use of such particles in various applications . To overcome this problem, modification of ferrite nanoparticles using suitable stabilizing ligands or coating materials (including small molecules, silica, polymers, carbon, ionic liquids, metal or metal oxide NPs, and their layer-by-layer combinations) has been proved to be the best solution to date . The modification techniques provide reaction sites or active groups for covalently grafting the active catalytic units onto the coated magnetic or ferrite nanoparticles to fabricate magnetically recoverable nanocatalysts . Silica is the most common material for coating the surfaces of ferrite nanoparticles; coating ferrite nanoparticles with silica avoids unfavorable contacts with the core, which both improves chemical stability and prevents particle aggregation , . The silica shell can be easily modified with different surface functional groups via covalent bonds between organo-silane molecules and silica shell. Dopamine derivatives, triethoxysilyl-, phosphonic acids-functionalized molecules, and glutathione were widely used to stabilize and functionalize MNPs . Triethoxysilyl-functionalized molecules such as commercially available NH2-, SH-, and Cl-terminatedcompounds and their further functionalized derivatives are another type of popular reagents for surface modification of MNPs . The linkage of MNPs with these silane reagents is achieved by coupling between the hydroxyl group of MNPs and silane reagent . Mesoporous carbon is another coating based on a main-group element that is used for MNPs. In this category, graphene oxide, carbon nanofibers, and carbon nanotubes (CNTs) have attracted special attention . The carbon layer can efficiently protect the spheres from dissolving in acidic environments because its dense structure can inhibit penetration of hydrogen ions . CNTs have rich surface functional groups (mainly hydroxyl and carboxyl), which made CNTs as a good support material for ferrite and metal oxide nanoparticles .
1.8 Characterizations of CoFe2O4 nanoparticles
The characterization of chemical and physical properties of ferrite nanoparticles including: the size of the particles, the shape of the particles, surface characteristics, the presence of any surface coating, and the presence of impurities is very important in catalysis science . Therefore, a series of spectroscopic techniques have been used to characterize cobalt ferrite nanoparticles.
Electron microscopy (transmission electron microscopy (TEM) and scanning electron microscopy (SEM): Since the size of ferrite materials is in the nano range (1–100 nm), TEM and SEM spectroscopic techniques are very important to determine the shape, size, and morphologies of nanoparticles .
High-resolution transmission electron microscopy (HR-TEM): HR-TEM is a more advanced technique that allows the observation of a single nanoparticle (<1 nm) and determination of its structural morphology .
Dynamic light scattering (DLS): DLS is a key spectroscopic technique to determine the average size diameter of the nanoparticles.
X-ray diffraction (XRD): XRD is a good spectroscopic technique to characterize crystalline phases, orientation, structural properties, and atomic arrangement of ferrite nanoparticles.
Inductive coupled plasma-atomic emission spectroscopy (ICP-AES): ICP-AES is a suitable spectroscopic technique to identify and determine metal composition in the nanomaterial or leaching of metals in the final nanomaterial .
Fourier transform infrared spectroscopy (FT-IR): FT-IR is an efficient spectroscopic technique to identify functional groups in nanomaterials, in particular functionalized nanocatalysts.
X-ray photoelectron spectroscopy (XPS): XPS is an effective spectroscopic technique to confirm the nature, binding energy, and oxidation state of nanomaterials.
N2 adsorption-desorption isotherms: A suitable spectroscopic technique to identify the Brunauer-Emmett-Teller theory (BET) surface area, pore volume, and average pore diameter.
Vibrating sample magnetometer (VSM): VSM is an efficient spectroscopic technique to determine the magnetic property of ferrite nanoparticles or functionalized magnetic nanocatalysts.
Energy-dispersive X-ray spectroscopy (EDS): EDS is a key spectroscopic technique to determine the percentage of elements or components in nanomaterials especially in functionalized nanocatalysts.
Thermogravimetric analysis (TGA): TGA is an effective spectroscopic technique to study both the thermal stability of nanomaterials and the bond formation between ferrite nanoparticles and catalyst.
2 Cobalt ferrite nanocatalysts in organic synthesis
In recent times, COFe2O4 nanocatalysts or cobalt ferrite-supported nanocatalysts have been successfully used in organic synthesis for a category of valuable reactions.
Oxidation catalysis is an important domain of chemical research. Oxidation catalysis not only plays a key role in the modern chemical industry for the production of valuable intermediates such as alcohols, epoxides, aldehydes, ketones, and organic acids but also will contribute to the establishment of novel green and sustainable chemical processes .
2.1.1 Alcohol oxidation
Carbonyl compounds are important structural scaffolds in the synthesis of biologically and pharmaceutically active molecules, polymers, and various other industrially important fine chemicals , . Selective oxidation of alcohols is the straightforward and most common route for the preparation of carbonyl compounds , . In 2014, Ramazani and his coworkers  have described a fascinating protocol for the oxidation of alcohols to the corresponding carbonyl compounds using magnetically recoverable and reusable CoFe2O4 nanoparticles (CF-MNPs 1). The structure of as-fabricated CF-MNPs 1 was characterized by FT-IR, SEM, and XRD spectroscopic techniques. Alcohol oxidation reactions were performed under aqueous medium at room temperature in the presence of oxone (potassium hydrogen monopersulfate) as oxidant. Under the described conditions, a library of primary and secondary benzylic and aliphatic alcohols (1 mmol) was smoothly oxidized to the corresponding carbonyl products in good to excellent yields (Scheme 1). The CF-MNPs 1 was magnetically recovered and reused for six cycles without noticeable loss of catalytic activity.
At the same time, Bhat and his research team immobilized nickel hydroxide complex on magnetic cobalt ferrite nanoparticles modified with 3-aminopropyltriethoxysilane (CoFe2O4@APTES@Ni(OH)2) (CF-MNPs 2) and successfully utilized this as a heterogeneous catalyst for the oxidation of alcohols to the carbonyl compounds. Synthesis steps of CF-MNPs 2 are designated in Scheme 2. As-prepared CF-MNPs 2 was characterized by FT-IR, atomic absorption spectrometry, XRD, SEM, TEM, energy-dispersive X-ray spectroscopy (EDX), and UV-vis spectroscopic techniques . The best reaction conditions for the alcohol oxidation was found to be CF-MNPs 2 as the catalyst and H2O2 (30 wt% in water, 10.0 mmol) as the oxidant in acetonitrile at 80°C. This catalytic system was able to oxidize primary and secondary alcohols (1 mmol) efficiently (87%) to corresponding carbonyls in good yields (Scheme 3). Conversion and selectivity were determined by GC. The CF-MNPs 2 could be reused several times with only a slightly decrease in activity.
In another study, Dhar and coworkers reported facile preparation of magnetic cobalt ferrite nanoparticles (CF-MNPs 3) (by a hydrothermal process). As-prepared CF-MNPs 3 was well characterized by XRD, TEM, BET, and SEM spectroscopic techniques. TEM analysis showed formation of spherical particles in sizes 2–30 nm. The CF-MNPs 3 was used as magnetically recoverable catalyst for the oxidation of alcohols (0.5 mmol) to the corresponding aldehydes by periodic acid (1 mmol) as oxidant . The reactions were performed in water at room temperature. A wide variety of benzylic and cyclic alcohols were oxidized to the target carbonyl products in high yields with tolerance of different functional groups (Scheme 4). The CF-MNPs 3 can be recovered and reused five times without significant decrease in reactivity.
Very recently, Shaabani et al. reported the fabrication of Cr and Zn-substituted cobalt ferrite nanoparticles supported on guanidine-grafted graphene oxide nanosheets, Zn-CoFe2O4@-G-GO (CF-MNPs 4), and Zn-CoFe2O4@-G-GO (CF-MNPs 5) as magnetically recoverable catalysts for the oxidation of alcohols. As-prepared catalysts were well confirmed by a series of characterization techniques such as FT-IR spectroscopy, XRD, UV-Vis, TGA, TEM, SEM, EDX, and BET spectroscopic techniques . Aerobic oxidation of alcohols (1 mmol) was carried out in o-xylene at 80°C. All results are listed in Table 1. The collected results in Table 1 revealed that both CF-MNPs 4 and CF-MNPs 5 (0.12 g) are efficient catalysts for the oxidation of alcohols to the corresponding carbonyl compounds. The catalysts could be reused five times without obvious decrease of the catalytic activity.
|Entry||Alcohol||CF-MNPs 4||CF-MNPs 5|
|Time (min)||Conversion (%)||Time (min)||Conversion (%)|
In order to show the efficiency of CF-MNPs catalysts, the obtained results for the oxidation of alcohols were compared with the previously reported procedures in the literature (Table 2). As shown in Table 2, CF-MNPs catalysts provide a favorable catalytic performance for the oxidation of alcohols compared to other catalysts (in terms of product yield, reusability, reaction time, and reaction conditions).
|1||CF-MNPs 1||19||6||15–240 min||70–99 |
|2||CF-MNPs 2||11||4||420 min||97–99 |
|3||CF-MNPs 3||11||6||50–90 min||84–98 |
|4||CF-MNPs 4||5||5||120 min||81–99 |
|5||CF-MNPs 5||5||5||150 min||76–97 |
|6||PW-MOF||26||4||120–420 min||14–98 |
|7||Au/TiO2||6||No||24–72 h||60–95 |
|8||Fe(NO3)3·9H2O/ABNO||26||No||2–12 h||47–99 |
|9||[RuH(CO)Cl(PPh3)3]||41||No||18–24 h||40–96 |
2.1.2 Hydrocarbon oxidation
Oxidation of hydrocarbons with molecular oxygen is an important transformation in chemistry science especially in chemical industry , . In 2009, Xia and his research team reported that magnetic CoFe2O4 nanocrystal (CF-MNPs 6) is an active heterogeneous catalyst for the aerobic oxidation of cyclohexane (37.3 mmol). The structure of CF-MNPs 6 was characterized by FT-IR, XRD, and TEM spectroscopic techniques. The TEM analysis of magnetic CoFe2O4 nanocrystal shows that the catalyst is formed of nanometer-sized particles (25–35 nm). After comprehensive experiments, aerobic oxidation under solvent-free conditions was considered as the standardized condition. As shown in Scheme 5, when pure CoFe2O4 was applied as catalyst (5 mg), 16.2% of cyclohexane conversion and 92.4% of selectivity for cyclohexanone and cyclohexanol were observed after 6 h. The catalyst can be readily recovered by an external magnet, and no significant loss of efficiency was observed when reused five successive times. CF-MNPs 6 was proved to be also efficient for oxidation of linear alkanes . Collected results are listed in Table 3.
|No||Substrate||Conversion (%)||Selectivity (%)|
|1||Pentane||3.1||2-Pentanone (56.3)||–||3-Pentanone (43.7)|
|2||Hexane||4.9||2-Hexanone (28.5)||–||3-Hexanone (71.5)|
|3||Heptane||5.7||2-Heptanone (62.4)||–||4-Heptanone (37.6)|
|4||Octane||9.1||2-Octanone (23.8)||3-Octanone (70.0)||4-Octanone (6.2)|
The selective oxidation of arenes to the corresponding aldehydes and ketones is one of the most important and useful transformations in organic synthesis, which has numerous applications in pharmaceutical, dyestuff, perfumery, and agrochemical industries , , . In 2012, Kooti and Afshari reported the immobilization of a Schiff base molybdenum complex on silica-coated cobalt ferrite nanoparticles (CF-MNPs 7) as a novel heterogeneous catalyst for the oxidation of alkenes. Stepwise preparation of the CF-MNPs 7 catalyst is shown in Scheme 6. Silica-coated cobalt ferrite nanoparticles were fabricated and functionalized with Schiff base groups to yield immobilized bidentate ligands. The functionalized MNPs were then reacted with Mo(O2)2(acac)2, resulting in the novel immobilized molybdenum Schiff base catalyst . The as-fabricated CF-MNPs 7 was characterized by FT-IR, SEM, TEM, TGA, XRD, and VSM spectroscopic techniques. The SEM and TEM images of Mo-salenSi@Si-CoFe2O4(CF-MNPs 7) show that the catalyst is formed of nanometer-sized particles (20–30 nm). The catalytic activity of CF-MNPs 7 (50 mg) was then tested in the oxidation of various alkenes (1 mmol) using 30% t-BuOOH as oxidant. The oxidation reactions are performed in 1,2-dichloroethane (5 ml) at 70°C. Collected results are listed in Table 4. As shown in Table 4, a series of alkenes and non-activated terminal olefin (1-octene) could be efficiently transformed to the corresponding products in admirable yields. The CF-MNPs 7 was also readily recovered and recycled (five times) with almost consistent activity.
|No||Alkenes||Product||Conversion (%)||Selectivity (%)||Time (h)|
In order to show the efficiency of CF-MNPs catalysts, the obtained results for the oxidation of hydrocarbons were compared with the previously reported procedures in the literature. Results are listed in Table 5.
2.2 Coupling reactions
Carbon-carbon and heteroatom (oxygen or sulfur) couplings are some of the most common and important reactions in organic synthetic chemistry , .
2.2.1 Carbon-carbon bond
Carbon-carbon cross-coupling is one of the most versatile reactions deployed in modern organic syntheses because it leads to the production of industrially, biologically, and pharmaceutically significant products . Suzuki cross-coupling reaction, also called Suzuki-Miyaura reaction, is one type of carbon-carbon coupling of aryl halides with arylboronic acids to produce asymmetric biaryls . In 2012, Phukan and his research team reported the fabrication of magnetically recoverable palladium catalyst through the direct addition of Pd nanoparticles during synthesis of cobalt ferrite nanoparticles. VSM, EDS, SEM, TEM, BET, and UV-vis spectroscopic techniques were utilized for the characterization of palladium catalyst (CF-MNPs 8) . The catalytic activity of the CF-MNPs 8 (2 mg) was evaluated in the Suzuki coupling of various aryl bromides or iodides (0.5 mmol) with arylboronic acids (0.75 mmol) in refluxing ethanol and in the presence of Na2CO3 (1.25 mmol) as base. Various bases and solvents were tested to obtain the optimized conditions. As depicted in Scheme 7, symmetrical and unsymmetrical biaryl derivatives were prepared with reasonable yields. Also, Pd catalyst could be reused for four times without any noticeable loss of catalytic activity.
2.2.2 Carbon-oxygen bond
Carbon-oxygen bond formation is arguably one of the most important coupling reactions in organic synthesis, because compounds containing C-O bonds (namely ethers) are significant solvents and synthetic important supplements for the production of fragrances, cosmetics, pharmaceuticals and dyestuffs , , . In a nice publication, Matloubi-Moghaddam and coworkers found that the C-O coupling reaction between various types of aryl halides (1 mmol) and phenol derivatives (1.1 mmol) can be successfully catalyzed by cobalt ferrite magnetic nanoparticles (CF-MNPs 9). Unfortunately, the characterization of cobalt ferrite catalyst was not reported. Amongst tested bases and solvents, K2CO3 (1.2 mmol) and DMF were found to be the best conditions for further investigation . As shown in Scheme 8, the C-O coupling reactions smoothly took place under the standardized conditions, and the ether products were obtained in venerable yields. It is noteworthy that aryl chlorides effectively participated in C-O coupling reactions, and the coupled products were afforded in high yields. Recycling of the CF-MNPs 9 was also checked in the coupling of bromobenzene and phenol, and only a slight loss of activity was observed after using eight times.
2.2.3 Carbon-sulfur bond
The syntheses of organosulfur compounds (compounds containing carbon-sulfur bonds) have aroused significant interest in the last decade as a result of their presence in natural products and pharmacologically and biologically active molecules , , , , . In this category (organosulfur compounds), sulfides occupy a very special place in organosulfur chemistry . The C-S cross-coupling reaction of aryl halides with thiols is an efficient strategy for the preparation of sulfides . In 2014, Zhou and his research team reported C-S coupling of 5-methyl-1,3,4-thiadiazol-2-thiol (0.2 mmol) with iodobenzene (0.24 mmol) catalyzed by CuI (0.01 mmol)/CF-MNPs 10 (0.02 mmol) system under K2CO3 (0.26 mmol) in DMF at 120°C . The sulfide product was afforded in 83% yield after 12 h.
In order to show the efficiency of CF-MNPs catalysts, the obtained results for the C-C and C-O coupling reactions were compared with the previously reported procedures in the literature. Results are listed in Table 6.
2.3 Heterocycles synthesis
Heterocyclic chemistry is one of the most important and valuable branches in chemistry science . Heterocycles are present in a broad library of drugs, most vitamins, many natural products, and biologically and industrially active molecules .
2.3.1 Five-membered heterocycles
Compounds containing pyrrole ring system are an important class of biologically and pharmaceutically active molecules; pyrrole derivatives possess many pharmacological properties and can play important roles in biochemical processes , . In 2014, Zhang and his research team designed a novel magnetically recoverable molybdenum catalyst via immobilization of molybdenum complex (Mo(acac)2) on the surface of silica-coated cobalt ferrite nanoparticles (CoFe2O4@SiO2) functionalized with 3-aminopropyltriethoxysilane under refluxing methanol conditions (Scheme 9). As-prepared CoFe2O4@SiO2-NH2-Mo(acac)2 (CF-MNPs 11) was well characterized by FT-IR, EDX, XRD, SEM, TEM, TGA, and VSM analysis . The activity of CF-MNPs 11 (1 mol%) was evaluated in one-pot, four-component synthesis of functionalized pyrrole derivatives. As shown in Scheme 10, four-component reaction of aldehydes (1 mmol), amines (1 mmol), 1,3-dicarbonyl compounds (1 mmol), and nitromethane (0.5 ml) have been conducted under thermal solvent-free conditions, and a nice category of polysubstituted pyrrole products were afforded in moderate to excellent yields. The CF-MNPs 11 can be recycled five times with a negligible decrease in activity.
In another report, Zhang and co-workers  have reported a new strategy to immobilize antimony (III) complex on surface of magnetic cobalt ferrite nanoparticles leading to a magnetically recoverable catalyst (CF-MNPs 12), which exhibits high catalytic efficiency in the synthesis of multisubstituted pyrroles. The general route involves the preparation of DABCO-functionalized silica-coated magnetic cobalt ferrite nanoparticles (CoFe2O4@SiO2-DABCO) upon reaction of DABCO ligand with magnetic CoFe2O4@SiO2 nanoparticles functionalized with 3-chloropropyltrimethoxysilane. Next, the reaction of CoFe2O4@SiO2-DABCO with antimony trichloride in refluxing acetone provided the final catalyst (CoFe2O4@SiO2-DABCO-Sb), as directed in Scheme 11. As-synthesized CF-MNPs 12 was subjected to characterize by several spectrum techniques such as FT-IR, EDX, XRD, SEM, and TEM spectroscopic techniques. Catalyst concentration and solvent type play a key role in the optimization of the reaction conditions. As shown in Scheme 12, CF-MNPs 12 (0.5 mol%) catalyzed the three-component reaction between amines (1 mmol), nitroolefins (1 mmol), and 1,3-dicarbonyl compounds (1 mmol) under refluxing ethanol, and a broad spectrum of N-protected functionalized pyrroles (48 examples) afforded in good to excellent yields. Reported results indicated the CF-MNPs 12 could be recycled for five runs without any loss of activity.
126.96.36.199 Imidazols and oxazoles
Imidazo[1,2-a]pyridines are an important class of N-heterocyclic compounds from the points of view of biological and pharmacological activities . In this respect, a magnetically copper complex supported on magnetic CoFe2O4 CNT (CoFe2O4/CNT-C) was fabricated, by Zhang and coworkers , and evaluated as a recoverable heterogeneous catalyst (CF-MNPs 13) for the synthesis of 3-nitro-2-arylimidazo[1,2-a]pyridines via one-pot three-component reaction of 2-aminopyridines (1 mmol), aldehydes (1 mmol), and nitromethane (1.1 mmol) in thermal PEG 400 under aerobic conditions. As shown in Scheme 13, the addition of CuCl complex to a suspension of magnetic CoFe2O4 CNT in water led to the generation of the target catalyst (CF-MNPs 13). As-synthesized CF-MNPs 13 was characterized by several spectroscopic techniques such as FT-IR, VSM, XRD, SEM, TEM, and EDX. The reaction failed in the absence of the catalyst. Several solvents such as PEG 400, H2O, EtOH, H2O/EtOH, DMF, CH3CN, CH2Cl2, toluene, and MeOH were tested, and water was found to be the best solvent. Under the described conditions, a nice collection of 3-nitro-2-arylimidazo[1,2-a]pyridines were synthesized in high yields (Scheme 14). The recovered catalyst was able to be recycled at least eight times without loss of activity.
Oxazoles and their derivatives have been recognized as key building blocks or synthetic intermediates for pharmaceutical and biological products , . In a nice publication, Hajipour and Khorsandi reported the synthesis of benzimidazoles and benzoxazoles through intramolecular C-O and C-N cross coupling reactions catalyzed by magnetic cobalt ferrite nanoparticles (CF-MNPs 14). The structure of as-prepared cobalt ferrite (CF-MNPs 14) was analyzed by FT-IR, SEM, TEM, EDX, ICP, and XRD spectroscopic techniques . To reach the standardized conditions, a number of solvents and bases were tested. It has been found that EtOH and K2CO3 (1.5 mmol) were the most efficient solvent and base, respectively. Under the standardized conditions, a library of benzimidazole and benzoxazole derivatives were prepared in moderate to excellent yields, as depicted in Schemes 15 and 16 . The CF-MNPs 14 could be easily recovered using an external magnet and reused several runs without significant loss of catalytic activity.
Thiazolidinone derivatives have been known to possess a library of biological activities, including antifungal, antimicrobial, and inflammatory activities , . Thiazolidinones are generally afforded via the three-component condensation between aldehydes with primary amines and mercaptoacetic acids. More recently, Safaei-Ghomi and his research group found that amine-functionalized silica-coated cobalt ferrite nanoparticles (CoFe2O4@SiO2/PrNH2) could be used as a highly efficient and magnetically recoverable catalyst (CF-MNPs 15) for the synthesis of 1,3-thiazolidin-4-ones. As shown in Scheme 17, CoFe2O4@SiO2/PrNH2 nanoparticles was prepared via the heterogenization of 3-aminopropyltriethoxysilane on silica-coated cobalt ferrite nanoparticles. FT-IR, SEM, and XRD spectroscopic techniques were applied for the characterization of as-prepared CF-MNPs 15 . Only a trace amount of the product was observed in the absence of a catalyst. A series of catalysts and solvents were examined to obtain the standardized conditions. A wide array of 1,3-thiazolidin-4-one derivatives were obtained in reasonable yields by reacting aldehydes (2 mmol) with anilines (2 mmol) and thioglycolic acid (2 mmol) in refluxing toluene for suitable times (120–140 min), as given in Scheme 18. The recovered catalyst could be reused eight times with only a slight decrease in activity.
In order to show the efficiency of CF-MNPs catalysts, the obtained results for the synthesis of pyrroles, imidazols, oxazoles, and thiazolidinones were compared with the previously reported procedures in the literature (Table 7). As shown in Table 7, CF-MNPs catalysts provide a favorable catalytic performance for the synthesis of pyrroles, imidazols, oxazoles, and thiazolidinones compared to other catalysts (in terms of product yield, reusability, reaction time, and reaction conditions).
|1||CF-MNPs 11||43||5||0.5–48 h||48–92 |
|2||CF-MNPs 12||48||5||0.25–24 h||47–92 |
|3||Clay K10||15||3||5–8 h||68–88 |
|4||NiO NPs||11||4||4 h||28–86 |
|5||CF-MNPs 13||20||8||3–6 h||80–96 |
|6||CF-MNPs 14||18||6||8–16 h||22–82 |
|7||CuI||11||No||5 h||34–75 |
|8||[Pd(allyl)Cl]2||40||No||24 h||46–88 |
|9||CF-MNPs 15||15||8||2–2.4 h||75–85 |
|10||Bi(SCH2COOH)3||11||No||2 h||70–90 |
|11||FeNi3||9||3||1.5 h||86–94 |
2.3.2 Synthesis of six-membered heterocycles
Pyridines are one of the most important classes of nitrogenated heterocycles with promising applications in diverse areas, such as pharmaceuticals, dyes, agrochemical molecules, and luminescence materials , , . In a nice publication, Zhang and his colleagues fabricated a novel organic inorganic hybrid heterogeneous catalyst by grafting chlorosulfuric acid on the surface of cobalt ferrite-graphene oxide that afforded magnetically recoverable graphene oxide-sulfonic acid (CoFe2O4-GO-SO3H) (CF-MNPs 16). Stepwise preparation of CF-MNPs 16 is designated in Scheme 19. First, graphene oxide (GO) was synthesized by oxidation of graphite powder according to a slightly modified Hummer’s method. The addition of chlorosulfonic acid into the CoFe2O4/GO suspension, formed from the reaction of graphene oxide with FeCl3, CoCl2 in the presence of ammonium hydroxide, in dichloromethane led to the preparation of CF-MNPs 16 . As-fabricated CF-MNPs 16 was characterized by XRD, VSM, SEM, and TEM spectroscopic techniques. The activity of CF-MNPs 16 catalyst was then investigated in the synthesis of 3,6-di(pyridin-3-yl)-1H-pyrazolo[3,4-b]pyridine-5-carbonitriles. Poor and moderate yields were observed when the reaction was catalyzed by CoFe2O4, GO, and CoFe2O4-GO. Three-component reactions of 1-phenyl-3-(pyridine-3-yl)-1H-pyrazol-5-amine (1 mmol), 3-oxo-3-(pyridine-3yl)propanenitrile (1 mmol), and aldehydes (1 mmol) catalyzed by CF-MNPs 16 (50 mg) in thermal ChCl/glycerol under microwave irradiation led to the desired products with excellent yields in <15 min, as shown in Scheme 20. Recycling studies have indicated that the CF-MNPs 16 can be easily recovered and reused for eight cycles with sustained activity.
Pyran derivatives are an important class of oxygenated-heterocyclic compounds with category of biological and pharmacological activities like anti-viral, antibacterial, and anti-inflammatory activities , , . A wide variety of 4-phenyl-4H-pyrano[3,2-h]quinolin-2-amine and 2-amino-4-phenyl-4H-pyrano[3,2-h] quinoline-3-carbonitrile derivatives was synthesized, by Sanasi and his research team, through three-component reaction of aromatic aldehydes (10 mmol), acetonitrile/malononitrile (10 mmol), and 8-hydoxyquinoline (10 mmol) catalyzed by magnetic nanocobalt ferrite (CF-MNPs 17) in EtOH under microwave irradiation (Scheme 21). The CF-MNPs 17 was prepared by sol-gel citrate precursor route and characterized by FT-IR, XRD, SEM, and TEM spectroscopic techniques . Catalyst concentration was studied to reach the standardized conditions. The catalyst can be recovered with an external magnet and reused repeatedly (five runs without any significant loss of catalytic activity).
In another report, Rajput and Kaur reported the synthesis of 2-amino-4-(phenyl)-5,6,7,8-tetrahydro-7, 7-dim ethyl-5-oxo-4H-pyrano-3-carbonitrile derivatives via cobalt ferrite nanoparticles (CF-MNPs 18)-catalyzed three-component reaction of aldehydes (2.5 mmol), 1,3-cyclic diketones (2.5 mmol), and active methylene compounds (malonitrile and ethyl acetoacetate) (2.5 mmol) under aqueous ethanol medium. As-prepared cobalt ferrite was characterized by XRD, VSM, and TEM spectroscopic techniques . Poor yield was observed in the absence of a catalyst. Moderate yields were obtained when the reaction was catalyzed by Fe3O4 and ZnO. By the catalytic system, a diverse range of the desired products was prepared in good to excellent yields and short times (in <20 min), as shown in Scheme 22. The CF-MNPs 18 could be recycled 10 times by magnetic separation without any decrease in the catalytic activity.
In order to show the efficiency of CF-MNPs catalysts, the obtained results for the synthesis of pyridines and pyrans were compared with the previously reported procedures in the literature (Table 8). As shown in Table 8, CF-MNPs catalysts provide a favorable catalytic performance for the synthesis of pyridines and pyrans compared to other catalysts (in terms of product yield, reusability, reaction time, and reaction conditions).
2.4 Other reactions
2.4.1 Ring-opening reaction of epoxides
The addition of nucleophiles to epoxides is one of the most significant and valuable asymmetric organic transformations in organic synthesis, which proposes numerous benefits in the fields of chemical and pharmaceutical industry , . The ring-opening reaction of epoxides with H2O2 is an efficient strategy for preparing β-hydroxy hydroperoxides (HHPs) (well known as compounds that possess antimalarial activity) , . In 2013, Zhang and his research team found that magnetic CoFe2O4 nanoparticles-supported phosphomolybdate ([CoFe2O4@SiO2-PrNH2-PMo]) is an efficient, green, and recoverable heterogeneous catalyst (CF-MNPs 19) for ring-opening of various epoxides (1 mmol) with ethereal hydrogen peroxide (5 ml). As shown in Scheme 23, the CoFe2O4@SiO2-PrNH2-PMo catalyst was prepared by anchoring 3-aminopropyltrimethoxysilane on magnetic CoFe2O4 nanoparticles, followed the reaction with phosphomolybdic acid in dry tetrahydrofuran under ultrasonic conditions. The catalyst characterization was performed by a series of techniques such as FT-IR, SEM, TEM, EDS, XRD, VSM, and ICP-MS analysis. The TEM analysis confirmed this topic that CoFe2O4@SiO2-PrNH2-PMo NPs have a core-shell structure and good dispersity . The catalytic activity of CF-MNPs 19 was evaluated in the ring-opening of epoxides with ethereal hydrogen peroxide (H2O2). In the absence of catalyst, only a trace amount of the product was observed even after 10 h. Under the standardized conditions (Scheme 24), the ring-opening reaction of epoxides with H2O2 was performed under mild conditions to give HHPs in respectable yields at ambient temperature . The recovered catalyst could be reused at least eight times with only a slight decrease in activity.
2.4.2 Knoevenagel condensation
Knoevenagel condensation is a well-known reaction in organic synthetic chemistry because the Knoevenagel products, namely, the α,β-unsaturated products or synthesized alkenes, play a key role in the synthesis of fine chemical, therapeutic drugs and heterocyclic compounds of biological importance , , . In 2011, Phukan et al. have described a fascinating and efficient protocol for the Knoevenagel condensation using magnetically recoverable and reusable CoFe2O4 nanoparticles (CF-MNPs 20). The prepared CF-MNPs 20 was fully characterized by FT-IR, XRD, EDS, BET, TGA, TEM, VSM, and electron spin resonance spectroscopic techniques. The average size of the CF-MNPs 20 from the TEM analysis was found to be 40–50 nm which is consistent with the particle size obtained from XRD analysis . The catalytic activity of CF-MNPs 20 was evaluated in Knoevenagel condensation of aldehydes (1 mmol) and ethylcyanoacetat (1 mmol). To identify the optimal conditions, the effect of catalyst loading and solvent nature was well studied. Under the standardized conditions, as shown in Scheme 25, a broad spectrum of aromatic aldehydes containing both electron-withdrawing and electron-donating groups reacted smoothly with ethylcyanoacetat under thermal water/ethanol, and the desired products were obtained in good to excellent yields (in <30 min). The CF-MNPs 20 can be magnetically recovered after the reaction and can be reused for four runs with only a minimal loss of activity (first run with 95% yield and fourth run with 88% yield).
2.4.3 Ritter reaction
Amides are key structural units in a variety of natural compounds and pharmacologically active molecules and display a broad range of biological activity , , . The Ritter reaction is a commonly used strategy for the preparation of amides . In 2014, Zhang and his colleagues evaluated the catalytic behavior of magnetic CoFe2O4 nanoparticle immobilized diamine-N-sulfamic acid (CoFe2O4@SiO2–DASA) in the synthesis of amides via the Ritter reaction under solvent-free conditions. Stepwise preparation of the CoFe2O4@SiO2-DASA is depicted in Scheme 26. CoFe2O4@SiO2-DA (CF-MNPs 21) was generated through the reaction of (N-(2-aminoethyl)-3-aminopropyl)tris-(2-ethoxy)silane with CoFe2O4@SiO2 in refluxing toluene. Amine groups tethered on the surface of CoFe2O4@SiO2 were treated with chlorosulfonic acid in CH2Cl2 to give the final catalyst (CoFe2O4@SiO2-DASA). The structure of CF-MNPs 21 was confirmed by a series of spectroscopic techniques such as FT-IR, XRD, SEM, TEM, and EDX spectroscopic techniques. EDX analysis confirmed the successful immobilization of sulfamic acid on CoFe2O4@SiO2 nanoparticles. The SEM and TEM images of CF-MNPs 21 show that the catalyst is formed of nanometer-sized particles (25–30 nm) . Ritter reaction failed in the absence of a catalyst. The catalyst concentration was a key factor to achieve the optimal conditions. As shown in Scheme 27, a broad spectrum of structurally diverse alcohols (1 mmol) and nitriles (1 mmol) was subjected to the Ritter reaction, and the target amides were furnished in high yields. The CF-MNPs 21 could be easily recovered by applying an external magnet and recycled for six runs without significant loss of its catalytic performance.
Formylation of amines is an important strategy of protecting a broad spectrum of amines and amino acids; the desired products, namely, formamides, are key intermediates in the synthesis of biologically and pharmaceutically active molecules , , . In 2015, Kooti and Nasiri reported the preparation of the magnetic CoFe2O4@SiO2-PTA catalyst (CF-MNPs 22) by the wet impregnation method, dissolving the phosphotungstic acid (PTA) on silica-coated cobalt ferrite nanoparticles (PTA) in aqueous medium (Scheme 28). The resultant CF-MNPs 22 was characterized by a series of spectroscopic techniques, including FT-IR, XRD, SEM, EDX, ICP-AES, and VSM. SEM and TEM analyses revealed uniformly sized MNPs with spherical morphology . The catalytic activity of CF-MNPs 22 was tested in the N-formylation of amines under solvent-free conditions at room temperature. As shown in Scheme 28, a wide range of aliphatic and aromatic amines was subjected to the N-formylation, and moderate to high yields of the desired formamides were obtained in <60 min. Easy recovery of the CF-MNPs 22 using an external magnet and high yields with up to five times make the protocol sustainable and economic.
2.4.5 Synthesis of 5-hydroxymethylfurfural
Finally, surface modification of cobalt ferrite nanoparticles with dicarboxylic acids (CoFe2O4@Carboxilic acid) as a magnetically recoverable acidic catalyst (CF-MNPs 23) for the synthesis of 5-hydroxymethylfurfural (HMF) have been published by Ranganath and his research team. The structure of CoFe2O4@Carboxilic acid was characterized by FT-IR, XRD, XPS, SEM, and TEM. TEM analysis of the CF-MNPs 23 shows that the average size of the catalyst was 11 nm in diameter and 18 nm after recyclability . As shown in Scheme 29, high conversion and good selectivity in the process was observed after 1 h. No significant loss of catalytic efficiency was consequently observed during the five consecutive reactions.
In order to show the efficiency of CF-MNPs catalysts, the obtained results for the alcoholysis of epoxides, Knoevenagel condensation, Ritter reaction, N-formylation, and synthesis of HMF were compared with the previously reported procedures in the literature (Table 9). As shown in Table 9, the reaction time and product yield is better than other protocols reported in literature. Also, the CF-MNPs catalyst is comparable in terms of stability, non-toxicity, and easy separation.
|1||CF-MNPs 19||14||8||15–30 min||78–92 |
|2||K5[CoW12O40]·3H2O||35||No||15–30 min||42–100 |
|3||ZrO(NO3)2 nH2O||11||3||20 min||78–97 |
|4||CF-MNPs 20||14||4||2–30 min||68–96 |
|5||NP-SnO2||16||7||1–3 h||80–96 |
|6||I2||16||No||2–90 min||70–98 |
|7||CF-MNPs 21||27||6||3–4 h||79–96 |
|8||TfOH||35||No||2–4 h||84–98 |
|9||In(OTf)3||14||No||24 h||48–97 |
|10||CF-MNPs 22||14||5||30–60 min||50–97 |
|11||Iridium||13||No||5–10 h||41–95 |
|12||MnO2||20||No||12 h||27–93 |
|13||CF-MNPs 23||1||5||1 h||96 |
|14||[AEMIM]BF4||1||No||8 h||68 |
3 Summary and outlook
The modern age of organic synthesis is changing towards the path of creative synthetic strategies which principally focus on environmental aspects of chemical or organic synthetic reactions such as the use of green materials and catalysts. Nowadays, magnetic separation has emerged as a robust, highly efficient, easy, and rapid separation technique for products and catalysts. Cobalt spinel ferrites (CoFe2O4) are attractive candidates due to their strong anisotropy, high coercivity, moderate saturation magnetization, and good mechanical and excellent chemical stabilities at higher temperature. The most important aspect in CoFe2O4 catalysis is the design and fabrication of a catalyst for specific organic reaction, considering the mechanistic pathway and the feasibility to perform reactions on a laboratory scale with potential for industrial applications . A broad library of high-pressure and high-temperature organic reactions can be carried out on nanomagnetite supported catalysts, because they are highly stable . Due to sturdy interaction between the support (MNPs) and metals, leaching of metal can be avoided or minimized . This review has submitted a comprehensive overview on the applications of recoverable cobalt ferrites nanocatalysts in a nice category of catalytic processes: oxidation, coupling, condensation, reduction, and multicomponent reactions. Amino-functionalized cobalt ferrite nanoparticles are the best support for the immobilization of metals and organocatalysts. A variety was first modified with amine ligands and was then reacted with metal complexes or acids to give the target nanocatalysts. These cobalt ferrite nanocatalysts possess a series of admirable advantages such as simple preparation, simplicity of operation, high catalytic activity, easy separation, and reusability. Accordingly, future attempts for more efficient protocols will still focus on the stability, sustainability, and environmental impacts due to the growing needs of the industry. These efforts enable a wide variety of industrial applications for cobalt ferrites nanocatalysts in the future.
About the authors
Mosstafa Kazemi was born in Ilam, Iran. He has received his MS degree in organic chemistry from Ilam University in 2013. He is presently preparing his PhD in the Nanosciences and Catalysis research group of Assistant Prof. Lotfi Shiriat at the Ilam University, where he is working on the synthesis and applications of magnetic nanoparticles-supported nanocatalysts in organic synthesis.
Massoud Ghobadi was born in Ilam, Iran. He has received his MS degree in inorganic chemistry from Ilam University in 2012. Currently, he is working towards his PhD under supervision of Assoc. Prof. Mohsen Nikoorazm at the Department of Chemistry of the Ilam University. His current interests are focused on the development of new strategies for the fabrication of heterogeneous nanocatalysts and their application in chemical reactions.
Ali Mirzaie was born in Ilam, Iran. He has received his MS degree in organic chemistry from Payame Noor University of Zanjan in 2013. His current interests are focused on the development of new strategies for the fabrication of heterogeneous nanocatalysts and their application in chemical reactions.
This work was supported by the research facilities of Islamic Azad University of Ilam, Iran.
 Shiri L, Ghorbani-Choghamarani A, Kazemi M. S-S bond formation: nano-catalysts in the oxidative coupling of thiols. Aust. J. Chem. 2017, 70, 9–25.10.1071/CH16318Search in Google Scholar
 Xu HJ, Wan X, Geng Y, Xu XL. The catalytic application of recoverable magnetic nanoparicles-supported organic compounds. Curr. Org. Chem. 2013, 17, 1034–1050.10.2174/1385272811317100006Search in Google Scholar
 Lim CW, Lee IS. Magnetically recyclable nanocatalyst systems for the organic reactions. Nano Today 2010, 5, 412–434.10.1016/j.nantod.2010.08.008Search in Google Scholar
 Dalpozzo R. Magnetic nanoparticle supports for asymmetric catalysts. Green Chem. 2015, 17, 3671–3686.10.1039/C5GC00386ESearch in Google Scholar
 Polshettiwar V, Luque R, Fihri A, Zhu H, Bouhrara M, Basset JM. Magnetically recoverable nanocatalysts. Chem. Rev. 2011, 111, 3036–3075.10.1021/cr100230zSearch in Google Scholar PubMed
 Kazemi M, Shiri L, Kohzadi H. Synthesis of pyrano [2,3,d] pyrimidines under green chemistry. J. Mater. Environ. Sci. 2017, 8, 3410–3422.Search in Google Scholar
 Wang D, Astruc D. Fast-growing field of magnetically recyclable nanocatalysts. Chem. Rev. 2014, 114, 6949–6985.10.1021/cr500134hSearch in Google Scholar PubMed
 Nasir-Baig RB, Varma RS. Magnetically retrievable catalysts for organic synthesis. Chem. Commun. 2013, 49, 752–770.10.1039/C2CC35663ESearch in Google Scholar PubMed
 Fadhel AZ, Pollet P, Liotta CL, Eckert CA. Combining the benefits of homogeneous and heterogeneous catalysis with tunable solvents and near critical water. Molecules 2010, 15, 8400–8424.10.3390/molecules15118400Search in Google Scholar PubMed PubMed Central
 Zhu Y, Stubbs LP, Ho F, Liu R, Ship CP, Maguire JA, Hosmane NS. Magnetic nanocomposites: a new perspective in catalysis. Chem. Cat. Chem. 2010, 2, 365–374.10.1002/cctc.200900314Search in Google Scholar
 Kazemi M, Shiri L. Recoverable bromine-containing nano- catalysts in organic synthesis. Mini Rev. Org. Chem. 2017, 14, DOI: 1.2174/1570193X14666170518114613.Search in Google Scholar
 Shiri L, Ghorbani-Choghamarani A, Kazemi M. Cu(II) immobilized on Fe3O4-diethylenetriamine: a new magnetically recoverable catalyst for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones and oxidative coupling of thiols. Appl. Organomet. Chem. 2017, 31, DOI: 10.1002/aoc.3596.Search in Google Scholar
 Shiri L, Ghorbani-Choghamarani A, Kazemi M. Sulfides synthesis: nanocatalysts in c–s cross-coupling reactions. Aust. J. Chem. 2016, 69, 585–600.10.1071/CH15528Search in Google Scholar
 Sadeghzadeh SM, Mogharabi M. Metal complexes immo-bilized on magnetic nanoparticles. Licensee InTech. 2016, 57–85.10.5772/61585Search in Google Scholar
 Cheng T, Zhang D, Li H, Liu G. Magnetically recoverable nanoparticles as efficient catalysts for organic transformations in aqueous medium. Green Chem. 2014, 16, 3401–3427.10.1039/C4GC00458BSearch in Google Scholar
 Shiri L, Ghorbani-Choghamarani A, Kazemi M. Synthesis and characterization of bromine source supported on magnetic Fe3O4 nanoparticles: a new, versatile and efficient magnetically separable catalyst for organic synthesis. Appl. Organomet. Chem. 2017, 31, DOI: 10.1002/aoc.3634.Search in Google Scholar
 Karimi B, Mansouri F, Mirzaei HM. Recent applications of magnetically recoverable nanocatalysts in C-C and C-X coupling reactions. Chem. Cat. Chem. 2015, 7, 1736–1789.10.1002/cctc.201403057Search in Google Scholar
 Zhang D, Zhou C, Sun Z, Wu LZ, Tunga CH, Zhang T. Magnetically recyclable nanocatalysts (MRNCs): a versatile integration of high catalytic activity and facile recovery. Nanoscale 2012, 4, 6244–6255.10.1039/c2nr31929bSearch in Google Scholar PubMed
 Gawande MB, Brancoa PS, Varma RS. Nano-magnetite (Fe3O4) as a support for recyclable catalysts in the development of sustainable methodologies. Chem. Soc. Rev. 2013, 42, 3371–3393.10.1039/c3cs35480fSearch in Google Scholar PubMed
 Ranganath KVS, Glorius F. Superparamagnetic nanoparticles for asymmetric catalysis – a perfect match. Catal. Sci. Technol. 2011, 1, 13–22.10.1039/c0cy00069hSearch in Google Scholar
 Shiri L, Rahmati S, Ramezani-Nejad Z, Kazemi M. Synthesis and characterization of bromine source immobilized on diethylenetriamine functionalized magnetic nanoparticles: a novel, versatile and highly efficient reusable catalyst for organic synthesis. Appl. Organomet. Chem. 2017, 31, DOI: 10.1002/aoc.3687.Search in Google Scholar
 Shiri L, Ghorbani-Choghamarani A, Kazemi M. Synthesis and characterization of tribenzyl ammonium-tribromide supported on magnetic Fe3O4 nanoparticles: a robust magnetically recoverable catalyst for the oxidative coupling of thiols and oxidation of sulfides. Res. Chem. Intermed. 2017, 43, 2707–2724.10.1007/s11164-016-2790-6Search in Google Scholar
 Kazemi M, Ghobadi M. Magnetically recoverable nano-catalysts insulfoxidation reactions. Nanotech. Rev. 2017, DOI:10.1515/ntrev-2016-0113.Search in Google Scholar
 Shiri L, Narimani H, Kazemi M. Synthesis and characterization of sulfamic acid supported on Fe3O4 nanoparticles: a green, versatile and magnetically separable acidic catalyst for oxidation reactions and Knoevenagel condensation. Appl. Organomet. Chem. 2017, DOI: 10.1002/aoc.3927.Search in Google Scholar
 Shiri L, Zarei S, Kazemi M, Sheikh D. Sulfuric acid heterogenized on magnetic Fe3O4 nanoparticles: a new and efficient magnetically reusable catalyst for condensation reactions. Appl. Organomet. Chem. 2017, DOI: 10.1002/aoc.3938.Search in Google Scholar
 Shiri L, Kazemi M, Heidari L. Magnetic Fe3O4 nanoparticles supported imine/thiophene-nickel (II) complex: a new and highly active heterogeneous catalyst for the synthesis of polyhydroquinolines and 2, 3-dihydroquinazoline-4(1H)-ones. Appl. Organomet. Chem. 2017, DOI: 10.1002/aoc.3943.Search in Google Scholar
 Shiri L, Kazemi M. Fe3O4 MNPs-DETA/Benzyl-Br3: a new magnetically reusable catalyst for the oxidative coupling of thiols. Phosphorus Sulfur Silicon Relat. Elem. 2017, 192, 1171–1176.10.1080/10426507.2017.1347654Search in Google Scholar
 Shiri L, Ghorbani-Choghamarani A, Kazemi M. Synthesis and characterization of DETA/Cu(NO3)2 supported on magnetic nanoparticles: a highly active and recyclable catalyst for the solvent-free synthesis of polyhydroquinolines. Monatsh. Chem. 2017, 148, 1131–1139.10.1007/s00706-016-1906-4Search in Google Scholar
 Shiri L, Kazemi M. Magnetic Fe3O4 nanoparticles supported amine: a new, sustainable and environmentally benign catalyst for condensation reactions. Res. Chem. Intermed. 2017, 43, 4813–4832.10.1007/s11164-017-2914-7Search in Google Scholar
 Shiri L, Narimani H, Kazemi M. Sulfamic acid immobilized on amino-functionalized magnetic nanoparticles: a new and active magnetically recoverable catalyst for the synthesis of N-heterocyclic compounds. Appl. Organomet. Chem. 2017, DOI: 10.1002/aoc.3999.Search in Google Scholar
 Kharisov BI, Rasika-Dias HV, Kharissova OV. Mini-review: ferrite nanoparticles in the catalysis. Arab. J. Chem. 2014, DOI: 10.1016/j.arabjc.2014.10.049.Search in Google Scholar
 Pang X, Fu W, Yang H, Zhu H, Xu J, Li X, Zou G. Preparation and characterization of hollow glass microspheres coated by CoFe2O4 nanoparticles using urea as precipitator via coprecipitation method. Mater. Res. Bull. 2009, 44, 360–363.10.1016/j.materresbull.2008.05.009Search in Google Scholar
 Manju K, Smitha T, Divya SN, Aswathy EK, Aswathy B, Arathy T, Binu-Krishna KT. Structural, magnetic, and acidic properties of cobalt ferrite nanoparticles synthesised by wet chemical methods. J. Adv. Ceram. 2015, 4, 199–205.10.1007/s40145-015-0149-xSearch in Google Scholar
 Swatsitang E, Phokha S, Hunpratub S, Usher B, Bootchanont A, Maensiri S, Chindaprasirt P. Characterization and magnetic properties of cobalt ferrite nanoparticles. J. Alloys Compd. 2016, 664, 792–797.10.1016/j.jallcom.2015.12.230Search in Google Scholar
 Soler MAG, Lima ECD, Silva SW, Melo TFO, Pimenta ACM, Sinnecker JP, Azevedo RB, Garg VK, Oliveira AC, Novak MA, Morais PC. Aging investigation of cobalt ferrite nanoparticles in low pH magnetic fluid. Langmuir 2007, 23, 9611–9617.10.1021/la701358gSearch in Google Scholar PubMed
 Wang B, Li B, Zhao B, Li CY. Amphiphilic Janus gold nanoparticles via combining “solid-state grafting-to” and “grafting-from ” methods. J. Am. Chem. Soc. 2008, 130, 11594–11595.10.1021/ja804192eSearch in Google Scholar PubMed
 Bueno AR, Gregori ML, Nobrega MCS. Ultrafast dynamics of 1 μm ZnO epitaxial films by time-resolved measurements. Mater. Chem. Phys. 2007, 105, 229–233.10.1016/j.matchemphys.2007.04.047Search in Google Scholar
 Sagadevan S, Podder J, Das I. Synthesis and characterization of cobalt ferrite (CoFe2O4) nanoparticles prepared by hydrothermal method. Recent Trends Mater. Sci. Appl. 2017, 145–152. DOI: 10.1007/978-3-319-44890-9_14.Search in Google Scholar
 Ding Z, Wang W, Zhang Y, Li F, Ping-Liu J. Synthesis, characterization and adsorption capability for Congo red of CoFe2O4 ferrite nanoparticles. J. Alloy. Compd. 2015, 640, 362–370.10.1016/j.jallcom.2015.04.020Search in Google Scholar
 Raghavender AT. Synthesis and characterization of cobalt ferrite nanoparticles. Sci. Technol. Arts. Res. J. 2013, 2, 1–4.10.4314/star.v2i4.1Search in Google Scholar
 Chagas CA, de Souza EF, de Carvalho MCNA, Martins RL, Schmal M. Cobalt ferrite nanoparticles for the preferential oxidation of CO. Appl. Catal. A. Gen. 2016, 519, 139–145.10.1016/j.apcata.2016.03.024Search in Google Scholar
 Zhou Z, Zhang Y, Wang Z, Wei W, Tang W, Shi J, Xiong R. Electronic structure studies of the spinel, CoFe2O4, by X-ray photoelectron spectroscopy. Appl. Surf. Sci. 2008, 254, 6972–6975.10.1016/j.apsusc.2008.05.067Search in Google Scholar
 Kooti M, Afshari M. Magnetic cobalt ferrite nanoparticles as an efficient catalyst for oxidation of alkenes. Sci. Iran. F 2012, 19, 1991–1995.10.1016/j.scient.2012.05.005Search in Google Scholar
 Gul IH, Maqsood A. Structural, magnetic and electrical properties of cobalt ferrites prepared by the sol-gel route. J. Alloy. Compd. 2008, 465, 227–231.10.1016/j.jallcom.2007.11.006Search in Google Scholar
 Wu X, Ding Z, Song N, Li L, Wang W. Effect of the rare-earth substitution on the structural, magnetic and adsorption properties in cobalt ferrite nanoparticles. Ceram. Int. 2016, 42, 4246–4255.10.1016/j.ceramint.2015.11.100Search in Google Scholar
 Yang Y, Jing L, Yu X, Yan D, Gao M. Coating aqueous quantum dots with silica via reverse microemulsion method: toward size-controllable and robust fluorescent nanoparticles. Chem. Mater. 2007, 19, 4123–4128.10.1021/cm070798mSearch in Google Scholar
 Sanpo N, Berndt CC, Wang J. Microstructural and antibacterial properties of zinc-substituted cobalt ferrite nanopowders synthesized by sol-gel methods. J. Appl. Phys. 2012, 112, 084333.10.1063/1.4761987Search in Google Scholar
 Sattar AA, EL-Sayed HM, Ibrahim ALS. Structural and magnetic properties of CoFe2O4/NiFe2O4 core/shell nanocomposite prepared by the hydrothermal method. J. Magn. Magn. Mater. 2015, 395, 89–96.10.1016/j.jmmm.2015.07.039Search in Google Scholar
 Yanez-Vilar S, Sanchez-Andujar M, Gomez-Aguirre C, Mira J, Senarıs-Rodrıguez MA, Castro-Garcıa S. A simple solvothermal synthesis of MFe2O4 (M=Mn, Co and Ni) nanoparticles. J. Solid. State. Chem. 2009, 182, 2685–2690.10.1016/j.jssc.2009.07.028Search in Google Scholar
 Molazemi M, Shokrollahi H, Hashemi B. The investigation of the compression and tension behavior of the cobalt ferrite magnetorheologi-cal fluids synthesized by co-precipitation. J. Magn. Magn. Mater. 2013, 346, 107–112.10.1016/j.jmmm.2013.06.053Search in Google Scholar
 Hu XG, Dong SJ. Metal nanomaterials and carbon nanotubes synthesis, functionalization and potential applications towards electro-chemistry. J. Mater. Chem. 2008, 18, 1279–1295.10.1039/b713255gSearch in Google Scholar
 Salunkhe AB, Khot VM, Phadatare MR, Pawar SH. Combustion synthesis of cobalt ferrite nanoparticles – influence of fuel to oxidizer ratio. J. Alloy. Compd. 2012, 514, 91–96.10.1016/j.jallcom.2011.10.094Search in Google Scholar
 Naseri MG, Saion EB, Ahangar HA, Shaari AH, Hashim M. Simple synthesis and characterization of cobalt ferrite nanoparticles by a thermal treatment method. J. Nanomat. 2010, 2010, 1–8.Search in Google Scholar
 Annie VP, Ansel ML, Emima JJ, Raja K, Queen-Sahaya TD, Fernandez AC, Krishnan S, Das JS. Investigations of optical, electrical and magnetic properties of cobalt ferrite nanoparticles by naive co-precipitation technique. Optik 2016, 127, 9917–9925.10.1016/j.ijleo.2016.07.063Search in Google Scholar
 Gawande MB, Monga Y, Zboril R, Sharma RK. Silica-decorated magnetic nanocomposites for catalytic applications. Coord. Chem. Rev. 2015, 288, 118–143.10.1016/j.ccr.2015.01.001Search in Google Scholar
 Shylesh S, Schnemann V, Thiel WR. Magnetically separable nanocatalysts: bridges between homogeneous and heterogeneous catalysis. Angew. Chem. Int. Ed. 2010, 49, 3428–3459.10.1002/anie.200905684Search in Google Scholar PubMed
 Mohapatra S, Rout SR, Panda AB. One-pot synthesis of uniform and spherically assembled functionalized MFe2O4 (M=Co, Mn, Ni) nanoparticles. Colloids Surf. A 2011, 384, 453–460.10.1016/j.colsurfa.2011.05.001Search in Google Scholar
 Shobaky GA, Turky A, Mostafa NY, Mohamed SK. Effect of preparation conditions on physicochemical, surface and catalytic properties of cobalt ferrite prepared by coprecipitation. J. Alloys. Compd. 2010, 493, 415–422.10.1016/j.jallcom.2009.12.115Search in Google Scholar
 Zhang M, Lu J, Zhang JN, Zhang ZH. Magnetic carbon nanotube supported Cu (CoFe2O4/CNT-Cu) catalyst: a sustainable catalyst for the synthesis of 3-nitro-2-arylimidazo[1,2-a]pyridines. Catal. Commun. 2016, 78, 26–32.10.1016/j.catcom.2016.02.004Search in Google Scholar
 Guo Z, Liu B, Zhang Q, Deng W, Wang Y, Yang Y. Recent advances in heterogeneous selective oxidation catalysis for sustainable chemistry. Chem. Soc. Rev. 2014, 43, 3480–3524.10.1039/c3cs60282fSearch in Google Scholar PubMed
 Bekhradnia AR, Zahir F, Arshadi S. Selective oxidation of organic compounds using pyridinium-1-sulfonate fluorochromate, C5H5NSO3H [CrO3F] (PSFC). Monatsh. Chem. 2008, 139, 521–523.10.1007/s00706-007-0720-4Search in Google Scholar
 Zhu J, Wang PC, Lu M. Selective oxidation of benzyl alcohol under solvent-free condition with gold nanoparticles encapsulated in metal-organic framework. Catal. A 2014, 477, 125–131.10.1016/j.apcata.2014.03.013Search in Google Scholar
 Vannucci AK, Hull JF, Chen Z, Binstead RA, Concepcion JJ, Meyer TJ. Water oxidation intermediates applied to catalysis: benzyl alcohol oxidation. J. Am. Chem. Soc. 2012, 134, 3972–3975.10.1021/ja210718uSearch in Google Scholar PubMed
 Lee AF, Ellis CV, Naughton JN, Newton MA, Parlett CMA, Wilson K. Reaction-driven surface restructuring and selectivity control in allylic alcohol catalytic aerobic oxidation over Pd. J. Am. Chem. Soc. 2011, 133, 5724–5727.10.1021/ja200684fSearch in Google Scholar PubMed
 Sadri F, Ramazani A, Massoudi A, Khoobi M, Azizkhani V, Tarasi R, Dolatyari L, Min B-K. Magnetic CoFe2O4 nanoparticles as an efficient catalyst for the oxidation of alcohols to carbonyl compounds in the presence of oxone as an oxidant. Bull. Korean Chem. Soc. 2014, 35, 2029–2032.10.5012/bkcs.2014.35.7.2029Search in Google Scholar
 Bhat PB, Inam F, Bhat BR. Nickel hydroxide/cobalt-ferrite magnetic nanocatalyst for alcohol oxidation. ACS Comb. Sci. 2014, 16, 397–402.10.1021/co500031bSearch in Google Scholar PubMed
 Paul B, Purkayastha DD, Dhar SS. One-pot hydrothermal synthesis and characterization of CoFe2O4 nanoparticles and its application as magnetically recoverable catalyst in oxidation of alcohols by periodic acid. Mat. Chem. Phys. 2016, 181, 99–105.10.1016/j.matchemphys.2016.06.039Search in Google Scholar
 Shaabani A, Hezarkhani Z, Keramati-Nejad M. Cr- and Zn-substituted cobalt ferrite nanoparticles supported on guanidine–modified graphene oxide as efficient and recyclable catalysts. J. Mater. Sci. 2017, 52, 96–112.10.1007/s10853-016-0314-9Search in Google Scholar
 Kazemi-Babahydari A, Fareghi-Alamdari R, Moradpour-Hafshejani S, Amiri-Rudbari H, Riahi-Farsani M. Heterogeneous oxidation of alcohols with hydrogen peroxide catalyzed by polyoxometalate metal–organic framework. J. Iran. Chem. Soc. 2016, 13, 1463–1470.10.1007/s13738-016-0861-7Search in Google Scholar
 Vindigni F, Dughera S, Armigliato F, Chiorino A. Aerobic oxidation of alcohols on Au/TiO2 catalyst: new insights on the role of active sites in the oxidation of primary and secondary alcohols. Monatsh Chem. 2016, 147, 391–403.10.1007/s00706-015-1616-3Search in Google Scholar
 Wang L, Shang S, Li G, Ren L, Lv Y, Gao S. Iron/ABNO-catalyzed aerobic oxidation of alcohols to aldehydes and ketones under ambient atmosphere. J. Org. Chem. 2016, 81, 2189–2193.10.1021/acs.joc.6b00009Search in Google Scholar PubMed
 Ray R, Chandra S, Maiti D, Lahiri GK. Simple and efficient ruthenium-catalyzed oxidation of primary alcohols with molecular oxygen. Chem. Eur. J. 2016, 22, 8814–8822.10.1002/chem.201601800Search in Google Scholar PubMed
 Labinger JA. Selective alkane oxidation: hot and cold approaches to a hot problem. J. Mol. Catal. A. Chem. 2004, 220, 27–35.10.1016/j.molcata.2004.03.051Search in Google Scholar
 Crabtree RH. Aspects of methane chemistry. Chem. Rev. 1995, 95, 987–1007.10.1021/cr00036a005Search in Google Scholar
 Tong J, Bo L, Li Z, Lei Z, Xia C. Magnetic CoFe2O4 nanocrystal: a novel and efficient heterogeneous catalyst for aerobic oxidation of cyclohexane. J. Mol. Catal. A. Chem. 2009, 307, 58–63.10.1016/j.molcata.2009.03.010Search in Google Scholar
 Mandi U, Pramanik M, Singha-Roy A. Chromium(VI) grafted mesoporous polyaniline as a reusable heterogeneous catalyst for oxidation reactions in aqueous medium. RSC Adv. 2014, 4, 15431–15440.10.1039/c3ra47884jSearch in Google Scholar
 Dhakshinamoorthy A, Alvaro M, Garcia H. Aerobic oxidation of styrenes catalyzed by an iron metal organic framework. ACS Catal. 2011, 1, 836–840.10.1021/cs200128tSearch in Google Scholar
 Nemanashi M, Meijboom R. Dendrimer derived titania-supported Au nanoparticles as potential catalysts in styrene oxidation. Catal. Lett. 2013, 143, 324–332.10.1007/s10562-013-0969-7Search in Google Scholar
 Kooti M, Afshari M. Molybdenum Schiff base complex covalently anchored to silica-coated cobalt ferrite nanoparticles as a novel heterogeneous catalyst for the oxidation of alkenes. Catal Lett. 2012, 142, 319–325.10.1007/s10562-012-0770-zSearch in Google Scholar
 Narayan-Biswas A, Das P, Kandar SK, Agarwala A, Bandyopadhyay D, Bandyopadhyay P. Chiral iron(III)-salen-catalyzed oxidation of hydrocarbons. Cat. Commun. 2009, 10, 708–711.10.1016/j.catcom.2008.11.023Search in Google Scholar
 Xiao Y, Liu J, Xie K, Wang W, Fang Y. Aerobic oxidation of cyclohexane catalyzed by graphene oxide: effects of surface structure and functionalization. Mol. Catal. 2017, 431, 1–8.10.1016/j.mcat.2017.01.020Search in Google Scholar
 Chinchilla R, Najera C. Recent advances in Sonogashira reactions. Chem. Soc. Rev. 2011, 40, 5084–5121.10.1039/c1cs15071eSearch in Google Scholar PubMed
 Gogoi P, Kalita M, Barman P. An efficient protocol for the carbon-sulfur cross-coupling of sulfenyl chlorides with arylboronic acids using a palladium catalyst. Synlett 2014, 25, 866–870.10.1055/s-0033-1340841Search in Google Scholar
 Sharm RK, Dutta S, Sharma S, Zboril R, Varma RS, Gawande MB. Fe3O4 (iron oxide)-supported nanocatalysts: synthesis, characterization and applications in coupling reactions. Green Chem. 2016, 18, 3184–3209.10.1039/C6GC00864JSearch in Google Scholar
 Li G, Jin R. Catalysis by gold nanoparticles: carbon-carbon coupling reactions. Nanotechnol Rev. 2013, 2, 529–545.10.1515/ntrev-2013-0020Search in Google Scholar
 Senapati KK, Roy S, Borgohain C, Phukan P. Palladium nanoparticle supported on cobalt ferrite: an efficient magnetically separable catalyst for ligand free Suzuki coupling. J. Mol. Catal. A Chem. 2012, 352, 128–134.10.1016/j.molcata.2011.10.022Search in Google Scholar
 Harkal S, Kumar K, Michalik D, Zapf A, Jackstell R, Rataboul F, Riermeier T, Monsees A, Beller A. An efficient catalyst system for diaryl ether synthesis from aryl chlorides. Tetrahedron Lett. 2005, 46, 3237–3240.10.1016/j.tetlet.2005.03.033Search in Google Scholar
 Yu JL, Wang H, Zou KF, Zhang JR, Gao X, Zhang W, Li ZT. Selective synthesis of unsymmetrical ethers from different alcohols catalyzed by sodium bisulfite. Tetrahedron 2013, 69, 310–315.10.1016/j.tet.2012.10.032Search in Google Scholar
 Kazemi M, Shiri L, Heidari L. A brief review: microwave assisted ethers synthesis. Org. Chem. Ind. J. 2016, 12, 1–6.Search in Google Scholar
 Matloubi-Moghaddam F, Tavakoli G, Aliabadi A. Application of nickel ferrite and cobalt ferrite magnetic nanoparticles in C-O bond formation: a comparative study between their catalytic activities. RSC Adv. 2015, 5, 59142–59153.10.1039/C5RA08146GSearch in Google Scholar
 Kazemi M, Kohzadi H, Abdi O. Alkylation of thiols in green mediums. J. Mater. Environ. Sci. 2015, 6, 1451–1456.Search in Google Scholar
 Kazemi M, Shiri L. Thioesters synthesis: recent adventures in the esterification of thiols. J. Sulfur Chem. 2015, 36, 613–623.10.1080/17415993.2015.1075023Search in Google Scholar
 Kazemi M, Shiri L, Kohzadi H. Recent achievements in organic trithiocarbonates synthesis. Phosphorus Sulfur Silicon Relat. Elem. 2015, 190, 1398–1409.10.1080/10426507.2014.993035Search in Google Scholar
 Kazemi M, Shiri L, Kohzadi H. Recent advances in aryl alkyl and dialkyl sulfide synthesis. Phosphorus Sulfur Silicon Relat. Elem. 2015, 190, 978–1003.10.1080/10426507.2014.974754Search in Google Scholar
 Liu Y, Zhou L, Hui X, Dong Z, Zhu H, Shao Y, Li Y. Fabrication of magnetic amino-functionalized nanoparticles for S-arylation of heterocyclic thiols. RSC Adv. 2014, 4, 48980–48985.10.1039/C4RA08782HSearch in Google Scholar
 Xing T, Zhang Z, Da YX, Quan ZJ, Wang XC. Ni-catalyzed Suzuki–Miyaura coupling reactions of pyrimidin-2-yl phosphates, tosylates and pivalates with arylboronic acids. Tetrahedron Lett. 2015, 56, 6495–6498.10.1016/j.tetlet.2015.10.009Search in Google Scholar
 Fujita K, Hattori H. Suzuki–Miyaura reaction catalyzed by a dendritic phosphine–palladium complex. Tetrahedron 2016, 72, 1485–1492.10.1016/j.tet.2016.01.048Search in Google Scholar
 Iranpoor N, Panahi F, Roozbin F, Rahimi S, Haghighi MG. Immobilized copper iodide on a porous organic polymer bearing P,N-ligation sites: a highly efficient heterogeneous catalyst for CO bond formation reaction. Molecul. Catal. 2017, 438, 214–223.10.1016/j.mcat.2017.06.008Search in Google Scholar
 Chen G, Chan ASC, Kwon FY. Palladium-catalyzed C–O bond formation: direct synthesis of phenols and aryl/alkyl ethers from activated aryl halides. Tetrahedron Lett. 2007, 48, 473–476.10.1016/j.tetlet.2006.11.036Search in Google Scholar
 Elwahy AHM, Shaaban MR. Synthesis of heterocycles and fused heterocycles catalyzed by nanomaterials. RSC Adv. 2015, 5, 75659–75710.10.1039/C5RA11421GSearch in Google Scholar
 Martins MAP, Frizzo CP, Moreira DN, Buriol L, Machado P. Solvent-free heterocyclic synthesis. Chem. Rev. 2009, 109, 4140–4182.10.1021/cr9001098Search in Google Scholar PubMed
 Martins MAP, Frizzo CP, Tier AZ, Moreira DN, Zanatta N, Bonacorso HG. Update 1 of: ionic liquids in heterocyclic synthesis. Chem. Rev. 2014, 114, 1–70. DOI: 10.1021/cr500106x.Search in Google Scholar PubMed
 Li BL, Zhang M, Hu HC, Du X, Zhang ZH. Nano-CoFe2O4 supported molybdenum as an efficient and magnetically recoverable catalyst for a one-pot, four-component synthesis of functionalized pyrroles. New J. Chem. 2014, 38, 2435–2442.10.1039/c3nj01368eSearch in Google Scholar
 Li BL, Hu HC, Mo LP, Zhang ZH. Nano CoFe2O4 supported antimony(III) as an efficient and recyclable catalyst for one-pot three-component synthesis of multisubstituted pyrroles. RSC Adv. 2014, 4, 12929–12943.10.1039/C3RA47855FSearch in Google Scholar
 Payra S, Saha A, Banerjee S. Nano-NiFe2O4 catalyzed microwave assisted one-pot regioselective synthesis of novel 2-alkoxyimidazo[1,2-a]pyridines under aerobic conditions. RSC Adv. 2016, 6, 12402–12407.10.1039/C5RA25540FSearch in Google Scholar
 Don MJ, Shen CC, Lin YL, Syu WJ, Ding YH, Sun CM. Nitrogen-containing compounds from Salvia miltiorrhiza. J. Nat. Prod. 2005, 68, 1066–1070.10.1021/np0500934Search in Google Scholar
 Easmon J, Purstinger G, Thies KS, Heinisch G, Hofmann J. Synthesis, structure−activity relationships, and antitumor studies of 2-benzoxazolyl hydrazones derived from alpha-(N)-acyl heteroaromatics. J. Med. Chem. 2006, 49, 6343–6350.10.1021/jm060232uSearch in Google Scholar
 Hajipour AR, Khorsandi Z. A comparative study of the catalytic activity of Co- and CoFe2O4-NPs in C–N and C–O bond formation: synthesis of benzimidazoles and benzoxazoles from o-haloanilides. New J. Chem. 2016, 40, 10474–10481.10.1039/C6NJ02293FSearch in Google Scholar
 Kavitha CV, Basappa CV, Swamy SN. Synthesis of new bioactive venlafaxine analogs: novel thiazolidin-4-ones as antimicrobials. Bioorg. Med. Chem. 2006, 14, 2290–2299.10.1016/j.bmc.2005.11.017Search in Google Scholar
 Barreca ML, Chimirri A, De Luca L. Discovery of 2,3-diaryl-1,3-thiazolidin-4-ones as potent anti-HIV-1 agents. Bioorg. Med. Chem. Lett. 2001, 11, 1793–1796.10.1016/S0960-894X(01)00304-3Search in Google Scholar
 Safaei-Ghomi J, Navvab M, Shahbazi-Alavi H. CoFe2O4@SiO2/PrNH2 nanoparticles as highly efficient and magnetically recoverable catalyst for the synthesis of 1,3-thiazolidin-4-ones. J. Sulf. Chem. 2016, 37, 601–612.10.1080/17415993.2016.1169533Search in Google Scholar
 Bharate JB, Sharma R, Aravinda S, Gupta VK, Singh B, Bharate SB, Vishwakarma RA. Montmorillonite clay catalyzed synthesis of functionalized pyrroles through domino four-component coupling of amines, aldehydes, 1,3-dicarbonyl compounds and nitroalkanes. RSC Adv. 2013, 3, 21736–21742.10.1039/c3ra43324bSearch in Google Scholar
 Gajengi AL, Bhanage BM. NiO nanoparticles: efficient catalyst for four component coupling reaction for synthesis of substituted pyrroles. Catal. Lett. 2016, 146, 1341–1347.10.1007/s10562-016-1762-1Search in Google Scholar
 Tang D, Wu P, Liu X, Chen YX, Guo SB, Chen WL, Li JG. Chen BH. Synthesis of multisubstituted imidazoles via copper-catalyzed [3+2] cycloadditions. J. Org. Chem. 2013, 78, 2746–2750.10.1021/jo302555zSearch in Google Scholar PubMed
 Tjutrins J, Arndtsen BA. A palladium-catalyzed synthesis of (hetero)aryl-substituted imidazoles from aryl halides, imines and carbon monoxide. Chem. Sci. 2017, 8, 1002–1007.10.1039/C6SC04371BSearch in Google Scholar
 Foroughifar N, Ebrahimi S. One-pot synthesis of 1,3-thiazolidin-4-one using Bi(SCH2COOH)3 as catalyst. Chin. Chem. Lett. 2013, 24, 389–391.10.1016/j.cclet.2013.03.019Search in Google Scholar
 Sadeghzadeh SM, Daneshfar F. Ionic liquid immobilized on FeNi3 as catalysts for efficient, green, and one-pot synthesis of 1,3-thiazolidin-4-one. J. Molecul. Catal. 2014, 199, 440–444.10.1016/j.molliq.2014.07.039Search in Google Scholar
 Ghaedi A, Bardajee GR, Mirshokrayi A, Mahdavi M, Shafiee A, Akbarzadeh T. Facile, novel and efficient synthesis of new pyrazolo[3,4-b]pyridine products from condensation of pyrazole-5-amine derivatives and activated carbonyl groups. RSC Adv. 2015, 5, 89652–89658.10.1039/C5RA16769HSearch in Google Scholar
 Chen JH, Liu WM, Ma JJ, Xu HT, Wu JS, Tang XL, Fan ZY, Wang PF. Synthesis and properties of fluorescence dyes: tetracyclic pyrazolo[3,4-b]pyridine-based coumarin chromophores with intramolecular charge transfer character. J. Org. Chem. 2012, 77, 3475–3482.10.1021/jo3002722Search in Google Scholar
 Patil SP, Shelar DP, Toche RB. Synthesis of pyrazolopyridine annulated heterocycles and study the effect of substituents on photophysical properties. J. Fluoresc. 2012, 22, 31–41.10.1007/s10895-011-0960-xSearch in Google Scholar
 Zhang M, Liu P, Liu Y, Shang Z, Hu H, Zhang Z. Magnetically separable graphene oxide anchored sulfonic acid: a novel, high efficient and recyclable catalystforone-potsynthesisof3,6-di(pyridin-3-yl)-1H-pyrazolo[3,4-b]pyridine-5-carbonitrilesin deep eutectic solvent under microwave irradiation. RSC Adv. 2016, 6, 106160–106170.10.1039/C6RA19579BSearch in Google Scholar
 Quintela JM, Peinador C, Moreira MJ. A novel synthesis of pyrano[2,3-d]pyrimidine derivatives. Tetrahedron 1995, 51, 5901–5912.10.1016/0040-4020(95)00258-ASearch in Google Scholar
 Wang JL, Liu D, Zhang ZJ, Shan S, Han X, Srinivasula SM, Croce CM, Alnemri ES, Huang Z. Structure-based discovery of an organic compound that binds Bcl-2 protein and induces apoptosis of tumor cells. Proc. Natl. Acad. Sci. 2000, 97, 7124–7129.10.1073/pnas.97.13.7124Search in Google Scholar PubMed PubMed Central
 Bandaru S, Majji RK, Bassa S, Chilla PN, Yellapragada R, Vasamsetty S, Jeldi RK, Korupolu RB, Sanasi PD. Magnetic nano cobalt ferrite catalyzed synthesis of 4H-pyrano[3,2-h]quinoline derivatives under microwave irradiation. Green Sustain. Chem. 2016, 6, 101–109.10.4236/gsc.2016.62009Search in Google Scholar
 Rajput JK, Kaur G. Synthesis and applications of CoFe2O4 nanoparticles for multicomponent reactions. Catal. Sci. Technol. 2014, 4, 142–151.10.1039/C3CY00594ASearch in Google Scholar
 Siddiqui ZN. Chitosan catalysed an efficient, one potsynthesis of pyridine derivatives. Tetrahedron Lett. 2015, 56, 1919–1924.10.1016/j.tetlet.2015.02.111Search in Google Scholar
 Ha PTM, Le BTT, To TC, Doan SH, Nguyen TT, Phan NTS. Synthesis of aryl-substituted pyridines via cyclization of N,N-dialkylanilines with ketoxime carboxylates under metal-organic framework catalysis. Ind. Eng. Chem. Res. 2017, 54, 151–161.10.1016/j.jiec.2017.05.028Search in Google Scholar
 Bhat AR, Shalla AH, Dongre RS. Synthesis of new annulated pyrano[2,3-d]pyrimidine derivatives using organocatalyst t (DABCO) in aqueous media. J. Saudi Chem. Soc. 2017, 21, S305–S310.10.1016/j.jscs.2014.03.008Search in Google Scholar
 Bhat AR, Selokar RS, Meshram JS, Dongre RS. Triethylamine: an efficient N-base catalyst for synthesis of annulated uracil derivatives in aqueous ethanol. J. Mater. Environ. Sci. 2014, 5, 1653–1657.Search in Google Scholar
 Cossy J, Bellosta V, Hamoir C, Desmurs JR. Regioselective ring opening of epoxides by nucleophiles mediated by lithium bistrifluoromethanesulfonimide. Tetrahedron Lett. 2002, 43, 7083–7086.10.1016/S0040-4039(02)01533-2Search in Google Scholar
 Aramesh N, Yadollahi B, Mirkhani V. Fe(III) substituted Wells–Dawson type polyoxometalate: an efficient catalyst for ring opening of epoxides with aromatic amines. Inorg. Chem. Commun. 2013, 28, 37–40.10.1016/j.inoche.2012.11.005Search in Google Scholar
 Hao HD, Li Y, Han WB, Wu YK. A hydrogen peroxide based access to qinghaosu (artemisinin). Org. Lett. 2011, 13, 4212–4215.10.1021/ol2015434Search in Google Scholar PubMed
 Singh C, Pandey S, Kushwaha AK, Puri SK. New functionalized 1,2,4-trioxepanes: synthesis and antimalarial activity against multi-drug resistant P. yoelii in mice. Bioorg. Med. Chem. Lett. 2008, 18, 5190–5193.10.1016/j.bmcl.2008.08.096Search in Google Scholar PubMed
 Li PH, Li BL, An ZM, Mo LP, Cui ZS, Zhang ZH. Magnetic nanoparticles (CoFe2 O4)-supported phosphomolybdate as an efficient, green, recyclable catalyst for synthesis of β-hydroxy hydroperoxides. Adv. Synth. Catal. 2013, 355, 2952–2959.10.1002/adsc.201300551Search in Google Scholar
 Freeman F. Properties and reactions of ylidenemalononitriles. Chem. Rev. 1980, 80, 329–350.10.1021/cr60326a004Search in Google Scholar
 Kraus GA, Krolski ME. Synthesis of a precursor to quassimarin. J. Org. Chem. 1986, 51, 3347–3350.10.1021/jo00367a017Search in Google Scholar
 Tietze LF. Domino reactions in organic synthesis. Chem. Rev. 1996, 96, 115–136.10.1002/9783527609925Search in Google Scholar
 Senapati KK, Borgohain C, Phukan P. Synthesis of highly stable CoFe2O4 nanoparticles and their use as magnetically separable catalyst for Knoevenagel reaction in aqueous medium. J. Mol. Catal. A Chem. 2011, 339, 24–31.10.1016/j.molcata.2011.02.007Search in Google Scholar
 Content S, Dupont T, Fedou NM, Smith JD, Twiddle SJR. Optimization of the manufacturing route to PF-610355 (1): synthesis of intermediate 5. Org. Process. Res. Dev. 2013, 17, 193–201.10.1021/op300341nSearch in Google Scholar
 Paulsen ES, Villadsen J, Tenori E, Liu HZ, Bonde DF, Lie MA, Bublitz M, Olesen C, Autzen HE, Dach I, Sehgal P, Nissen P, Moller JV, Schiott B, Christensen SB. Water-mediated interactions influence the binding of thapsigargin to sarco/endoplasmic reticulum calcium adenosinetriphosphatase. J. Med. Chem. 2013, 56, 3609–3619.10.1021/jm4001083Search in Google Scholar PubMed
 Guerinot A, Reymond S, Cossy J. Ritter reaction: recent catalytic developments. Eur. J. Org. Chem. 2012, 2012, 19–28.10.1002/ejoc.201101018Search in Google Scholar
 Zhao XN, Hu HC, Zhang FJ, Zhang ZH. Magnetic CoFe2O4 nanoparticle immobilized N-propyl diethylenetriamine sulfamic acid as an efficient and recyclable catalyst for the synthesis of amides via the Ritter reaction. Appl. Catal. A Gen. 2014, 482, 258–265.10.1016/j.apcata.2014.06.006Search in Google Scholar
 Kim JG, Jang DO. Facile and highly efficient N-formylation of amines using a catalytic amount of iodine under solvent-free conditions. Synlett 2010, 14, 2093–2096.10.1002/chin.201102045Search in Google Scholar
 Kima JG, Jang DO. Indium-catalyzed N-formylation of amines under solvent-free conditions. Synlett 2010, 8, 1231–1234.10.1055/s-0029-1219784Search in Google Scholar
 Ortega N, Richter C, Glorius F. N-formylation of amines by methanol activation. Org. Lett. 2013, 15, 1776–1779.10.1021/ol400639mSearch in Google Scholar PubMed
 Kooti M, Nasiri E. Phosphotungstic acid supported on silica-coated CoFe2O4 nanoparticles: an efficient and magnetically-recoverable catalyst for N-formylation of amines under solvent-free conditions. J. Mol. Catal. A Chem. 2015, 406, 168–177.10.1016/j.molcata.2015.05.009Search in Google Scholar
 Shaikh M, Sahu M, Atyam KK, Ranganath KVS. Surface modification of ferrite nanoparticles with dicarboxylic acids for the synthesis of 5-hydroxymethylfurfural: a novel and green protocol. RSC Adv. 2016, 6, 76795–76801.10.1039/C6RA13354ASearch in Google Scholar
 Tangestaninejad S, Moghadam M, Mirkhani V, Yadollahi B, Mirmohammadi MR. Mild and efficient ring opening of epoxides catalyzed by potassium dodecatungstocobaltate(III). Monatsh. Chem. 2006, 137, 235–242.10.1007/s00706-005-0415-7Search in Google Scholar
 Shinde SS, Said MS, Surwase TB, Kumar P. Mild regiospecific alcoholysis and aminolysis of epoxides catalyzed byzirconium(IV) oxynitrate. Tetrahedron Lett. 2015, 56, 5916–5919.10.1016/j.tetlet.2015.09.031Search in Google Scholar
 Sharghi H, Ebrahimpourmoghaddam S, Memarzadeh R, Javadpour S. Tin oxide nanoparticles (NP-SnO2): preparation, characterization and their catalytic application in the Knoevenagel condensation. J. Iran. Chem. Soc. 2013, 10, 41–149.10.1007/s13738-012-0135-ySearch in Google Scholar
 Ren Y, Cai C. Iodine catalysis in aqueous medium: an improved reaction system for Knoevenagel and Nitroaldol condensation. Catal. Lett. 2007, 118, 134–138.10.1007/s10562-007-9169-7Search in Google Scholar
 Singh G, Dada R, Yaragorla S. TfOH catalyzed one-pot Schmidt-Ritter reaction for the synthesis of amides through N-acylimides. Tetrahedron Lett. 2016, 5, 4424–4427.10.1016/j.tetlet.2016.08.069Search in Google Scholar
 Posevins D, Suta K, Turks M. Indium-triflate-catalyzed Ritter reaction in liquid sulfur dioxide. Eur. J. Org. Chem. 2016, 2016, 1414–1419.10.1002/ejoc.201600013Search in Google Scholar
 Saidi O, Bamford MJ, Blacker AJ, Lynch J, Marsden SP, Plucinski P, Watson RJ, Williams JMJ. Iridium-catalyzed formylation of amines with paraformaldehyde. Tetrahedron Lett. 2010, 51, 5804–5806.10.1016/j.tetlet.2010.08.106Search in Google Scholar
 Yedage SL, D’silva DS, Bhanage BM. MnO2 catalyzed formylation of amines and transamidation of amides under solvent-free condition. RSC Adv. 2015, 5, 80441–80449.10.1039/C5RA13094HSearch in Google Scholar
 Qu Y, Li L, Wei Q, Huang C, Oleskowicz-Popiel P, Xu J. One-pot conversion of disaccharide into 5-hydroxymethylfurfural catalyzed by imidazole ionic liquid. Sci Rep. 2016, 6, 1–7.10.1038/srep26067Search in Google Scholar PubMed PubMed Central
©2017 Walter de Gruyter GmbH, Berlin/Boston
This article is distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.