Preparation of benzylidene compounds

摘要

A process for the preparation of a benzylidene compound of the formula in which R1 is hydrogen or one or two substituents independently selected from the group consisting of nitro, cyano, halogen, SO3H, alkyl, alkoxy and fluorinated alkyl, each with 1 to 4 C atoms and two or three fluorine substituents, and R3 is alkyl with 1 to 10 C atoms, which is optionally interrupted by an oxygen in the chain or is optionally substituted by fluorine, chlorine, hydroxyl or a methylbenzylamine group, comprising reacting an acetal of the formula in which R2 each independently is alkyl with 1 to 6 C atoms, which is optionally substituted by phenyl, or the two radicals R2 conjointly form an alkylene radical with 1-6 C atoms, with a beta -ketocarboxylic acid ester of the formula CH3CO-CH2-COOR3 in the presence of an acid at a temperature between about 40 DEG and 120 DEG .