R 30 Steric structure of alkyl 2-aryl(hetaryl)hydrazono-3-fluoroalkyl-3-oxopropionates [Electronic resource] / E. V. Shchegol'kov, Ya. V. Burgart, O. G. Khudina, V. I. Saloutin, O. N. Kazheva, A. N. Chekhlov // Russian Journal of Organic Chemistry (Translation of Zhurnal Organicheskoi Khimii). - 2009. - Vol. 45, № 6. - P801-809 Рубрики: ХИМИЧЕСКИЕ НАУКИ Аннотация: Steric structure of fluorinated 2-arylhydrazono-3-oxo esters was studied by 1H, 19F, and 13C NMR spectroscopy and X-ray analysis. It was found that these compounds in the crystalline state and in solutions in acetone-d 6, DMSO-d 6, and CDCl3 exist as Z isomers with the ester fragment involved in intramolecular hydrogen bond with the hydrazone NH proton. Exceptions are alkyl 2-arylhydrazono-4,4-difluoro-3-oxobutanoates which exist in acetone-d 6 as mixtures of Z and E isomers, the former prevailing. Unlike fluorinated analogs, ethyl 2-(4-methylphenyl)hydrazono-3-oxobutanoate in crystal has the structure of E isomer in which intramolecular hydrogen bond is formed between the NH proton and acetyl carbonyl group. The same compound in acetone-d 6, DMSO-d 6, and CDCl3 gives rise to a mixture of Z and E isomers, the latter prevailing \\\\Expert2\\nbo\\Russian Journal of Organic Chemistry\\2009, 45 (6), 801.pdf |