The mechanism of formation of alkene stereoisomers in the catalytic olefination reaction of carbonyl compounds was studied. 4-Chlorobenzaldehyde hydrazone 1 stereoselectively reacts with a number of F-, Cl-, Br-, and I-containing polyhaloalkanes in the presence of catalytic amounts of CuCl to give omega-substituted styrenes 2 with the more thermodynamically stable alkene isomer being the major product. A model for the formation of the stereoisomers of alkenes 2 in the olefination reaction is proposed. Stereoselectivity of the reaction is determined by elimination of copper(II) halides from the lowest-lying conformers of organocopper intermediates II. According to quantum-chemical calculations, the elimination should involve the staggered conformations with antiperiplanar arrangement of C-Hal and C-Cu bonds and proceed by the E2 anti-elimination mechanism. The results of quantum-chemical calculations are in good agreement with the experimental E/Z alkene isomer ratios.
作者:Valentine G. Nenajdenko、Alexey V. Shastin、Vasily N. Korotchenko、Georgy N. Varseev、Elisabeth S. Balenkova
DOI:10.1002/ejoc.200390033
日期:2003.1
A new general catalytic olefination reaction (COR) of aromatic and heteroaromatic aldehydes and ketones was applied to synthesise 2-chloro-2-fluorostyrenes. The two-stage procedure includes the transformation of carbonyl compounds into hydrazones followed by treatment with CFCl3 mediated by copper catalysis. Trichlorofluoromethane was used as a chlorofluoromethylene transfer reagent. The reaction proceeds
作者:V. N. Korotchenko、A. V. Shastin、V. G. Nenaidenko、E. S. Balenkova
DOI:10.1023/a:1026007801456
日期:——
Hydrazones of carbonyl compounds at treatment with polyhaloalkanes in the presence of CuCl as catalyst are converted into substituted alkenes with formation of a new C=C bond.