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calculations and comparison with the UPS spectra of related compounds. An unusual π-or- bital degeneracy in this molecule of C2-symmetry was observed. The spiroconjugation is quenched, and the reasons are discussed. Key words: Spiroconjugation; Photoelectron Spectroscopy. 1. Introduction The intramolecular interaction between nonconju- gated π orbitals is of considerable interest and was studied by UV photoelectron spectroscopy (UPS) in many molecules [1]. The presence of interaction is in- dicated by the splitting of π bands when compared with π ionizations in the fragment

The synthesis of substituted diaza [4.4] spirenes (3) by 1.3-dipolar addition of diazo-cyclopentadienes to alkynes is described. If the 1- or 4-position of the diazo-cyclopentadienes contains an H-atom, bicyclic pyridazine derivatives are formed with alkynes. The uv-spectra of the diaza [4.4] spirenes (3) are discussed with regard to the new term “spiroconjugation”.

.): International Tables for Crystallography, Vol. A, 4th Ed., Kluwer Academic Publishers, Dordrecht/Boston/London, 1995. [6] L. Euler: “Elementa doctrinae solidorum and Demonstratio nonnularum insignium proprietatum quibus solida heddris planis inclusa sunt praedita”, Proceedings of the St. Petersburg Academy, 1758. [7] A.F. Wells: Three Dimensional Nets and Polyhedra, 1st Ed., John Wiley and Sons Inc., New York, 1977. [8] M.J. Bucknum: “Effects of Spiroconjugation in the Electronic Band Structure of Glitter”, Carbon, Vol. 35(1), (1997). [9] M. Henle: A Combinatorial

References 1 1997 3 66 255 10.1070/RC1997v066n03ABEH000233 Shapiro Boris I Russian Chemical Reviews RUSS CHEM REV 14684837 Chemical problems of the infrared sensitisation of photographic materials 2 1997 5 70 1109 10.1246/bcsj.70.1109 Katoh Takashi Ogawa Keizo Inagaki Yoshio Okazaki Renji Bulletin of the Chemical Society of Japan Bull Chem Soc Jpn 13480634 Evidence for Spiro-Conjugation in Perpendicularly-Linked Pentamethinestreptocyanine Dimers. 3 1997 9 70 2279 10.1246/bcsj.70.2279 Katoh Takashi Inagaki Yoshio Okazaki Renji Bulletin of the Chemical Society of

-Zn-Bi] 4− – a linear polyanion iso (valence) electronic to CO 2 Angew. Chem 126 2014 9090 9094 Angew. Chem. Int. Ed. 53 (2014) 8944–8948. 12 Resa, I.; Carmona, E.; Gutierrez-Puebla, E.; Monge, A.: Decamethyldizincocene, a stable compound of Zn(I) with a Zn-Zn Bond. Science 305 (2004) 1136–1138. 10.1126/science.1101356 15326350 Resa I. Carmona E. Gutierrez-Puebla E. Monge A. Decamethyldizincocene, a stable compound of Zn(I) with a Zn-Zn Bond Science 305 2004 1136 1138 13 Haumann, T.; Benet-Buchholz, J.; Boese, R.: Structural effects of spiroconjugation: crystal

(stellane) as building block. The syntheses of a number of model systems such as 2,6-stelladiene, 2,4,6- stellatriene and 2,2’,6,6-distellatriene are discussed. By means of He( I ) photoelectron spectroscopy the interaction between the x-systems has been investigated. It is found that the stellane skeleton is a good relay. The interaction between two x-systems can be classified into conjugation, homoconjugation, spiroconjugation and through bond interaction ( f ) . If both x-systems are directly linked, as in l,Sbutadiene, we talk about conjugation. If the x

Pure c Appi. Chem., Vol.52, pp.1431—1441. Pergatnon Press Ltd. 1980. Printed in Great Britain. ASPECTS OF CYCLIC CONJUGATION Michael J. S. Dewar* and Mtchael L. McKee Department of Chemistry, The University of Texas at Austin Austin, Texas 78712 Abstract - (a) The usefulness of PMO theory as a guide to chemical behaviour is illustrated by its application to spiro- conjugation. It is shown in this way that spiroconjugation can be chemically important only in the case of spiro [3,3] heptadieniyl which may be sufficiently stabilized to exist as a monomeric

. Though not yet experimentally achieved these cases are theoretically amus- ing, and I would like to recount the story of three such systems to you. THE SPIRARENES AND SPIROCONJUGATION The well known molecular orbitals ofan allyl system are shown in Figure 1. If two allyl radicals are brought tagether in such a way as to produce little interaction among the energy Ievels then the ground state of the system of the two radicals is likely to be a triplet. If the radicals are brought tagether so that the Ievels interact appreciably then it is possible that the

. Using this value we can estimate the homo-aromatic stabilization (ASE) of 8 as follows: 0 ;ll.H,- 25.7kcaljmole 8 --+ 9; ll.H, + 10.2 kcaljmole (12) The difference between the two values (35.9 kcaljmole) should be equal to a sum of the strain energy in 9 plus the ASE of 8. Since it seems unlikely that the strain energy of 9 could be much greater than that of cyclopropane (27 kcaljmole), the homoconjugative stabilization of 8 must be significant, probably close to 9 kcaljmole. The second problem, that of spiroconjugation, was studied by calculating the heats

Introduction Unique properties of spiro heterocyclic compounds are spiroconjugation, spirohyperconjugation, and anomeric effect. Because their special space configurations can usually match different spatial structures of macromolecules in organisms, these compounds can show significant biological activity [1]. The spiro compounds are widely used as a pharmacophore unit in the synthesis of antineoplastic [2], antidepressant [3, 4], antiviral [5], antibacterial [6], and antianxiety [7–9] drugs. Spiro[3,3]heptane and its derivatives has recently been used as the