| abstract |
Prodn. of polyenecarbonyl cpds. (I) having high all-E content, and their acetals and ketals, comprises reacting a carbonyl cpd. (II) with a dialkyl phosphonate in a Horner-Emmons reaction or with a CH-acidic cpd. in an aldol condensation in the presence of 0.3-10 mol.% (based on (II)) of a component (B) comprising a) oxygen or nitrogen monoxide (opt. mixed with an inert gas); b) the stable 2,2-diphenyl-1-picrylhydrazyl radical or a hydrogen peroxide-urea adduct; c) quinone, a quinone deriv. or coenzyme Q10 hydroquinone; and/or d) a stable radical of formula (I) or (II). R1, R2 = 1-4C alkyl; or R1+R2 = ethylene, propylene, vinylene or propenylene (all opt. substd. by alkyl, aryl, OH, alkoxy, silyloxy, oxo, NH2, SH, alkylthio, CN, COOH, carbamoyl, heteroaryl or alkylcarbonyloxy); R3-R5 = as R1, R2. |