The preparation of the title compounds from aldehyd-aniles and alkylnitroacetates in acetic anhydride is described. The nitrocinnamates, which in solution are mixtures of the E- and Z-isomers, are studied PMR-spectroscopically, using Eu(fod)3 as a shift reagent. A simple method for the signal assignment is worked out, making it unnecessary to prepare pure diastereomers.
Fluorescence data of 3-ethoxycarbonyl-, 3-acetyl-, 3-phephyl-, 4-methyl-3-phenyl-, 3-(2-benzothiazolyl) -and 3-cyanosubstituted 7-hydroxycoumarines are reported as a function of acidity (pH 0 - 9). Unlike umbelliferone or its 4-methyl derivative they do not exhibit significant photoautomerism in acidified solutions, but with the exception of the benzothiazolyl derivative. This behaviour can be interpreted in terms of a) steric hindrance by the substituent and b) enhanced charge delocalisation in the first excited singlet state, leading to lower basicities at the ring carbonyl oxygen.
The synthesis of three new reagents, namely the bromomethyl derivatives of a pyrano-[3,2-c]benzopyran (2b) and of 11H-pyrido[1,2-b]quinazolin-11-one (3b, d) is described. Introduction of the reactive bromomethyl group was accomplished in one case (2 b) by a ring closure reaction using ethyl y-chloroacetoacetate, and in the other cases (3 b, d) by bromination of a methyl group using N-bromosuccinimide. 2 b is suitable for the derivatization of barbiturates, whilst 3d reacts with oxygen nucleophiles like alcohols, phenols or carboxylates.
Three component condensation of active methylene compounds with aniline and trialkyl orthoformate gives anilinomethylene-1,3-dicarbonyls, which can be hydrolysed with aqueous K2CO3, KOH or HCl, depending on the sensitivity of the hydroxymethylene derivative thus formed. The reactions sequence is fairly generally applicable: Cyclohexan-1,3-diones, pyrimin-3,5-diones (including barbituric acids), pyrazolones and pyrazolin-3,5-diones, indan-1,3-dione, (thio)phthalide, indoxyl, oxindole, anthrone, 2,6- and 2,7-dihydroxynaphthalene, and pentan-2,4-dione have been formylated. Using orthoacetate or orthopropionate, tetronic acid, pyrazolones and pyrazolin-3,5-diones,resp.,could also be acylated by this method.
Reaction of active methylene compounds (2,4-pentanedione, dimedone, 4-hydroxycoumarin, 4-hydroxycarbostyriles) with triethyl orthoformate and primary amines (aniline, o-methylmercapto aniline, cyclohexylamine) yields substituted aminomethylen-1.3-dicarbonyles (1-5), which in their tautomeric form (B) give stable, deeply coloured Cu··- and Ni- --organic complexes (6-27). The same chelates may also be obtained by direct reaction of orthoformate, amine and active methylene in the presence of the metal acetate at 40-50 °C in 65-90% yield.
Anilinomethylene-3-methyl-1-phenylpyrazolone in turn does not exhibit any tendency to chelate Cu·· or Ni··. The X-ray crystallography of its o-methylmercaptoderivative shows it to exist in the virtually planar enamin form.
The combined action of orthoformate and aniline upon cyclohexanedione-1,3 yields anilinomethylene-cyclohexanedione-1,3, which react with cyanoacetate or malodinitrile in DMF in the presence of KOH to give ethyl-1-phenyl-2,5-dioxo-1,2,5,6,7,8-hexahydroquinoline-3-carboxylates (or -carbonitrils)
The combined action of orthoformate and aniline upon 4-hydroxy-coumarin yields anilinomethylene chromon-2,4-dione, which reacts with ethyl cyanoacetate in DMF in the presence of KOH to give the pyronocoumarine (6a). Pyronoquinolones are obtained in a similar way.