PROCESS FOR PREPARING ALKYL 2-ALKOXYMETHYLENE-4,4-DIFLUORO-3-OXOBUTYRATES

摘要

A process for preparing alkyl 2-alkoxymethylene-4,4-difluoro-3-oxobutyrates (VI) where R is methyl or ethyl, from crude reaction mixtures of alkyl 4,4-difluoroacetoacetates (I) by a) reacting alkyl acetate (II), RO M alkoxide (III), where M is a sodium or potassium ion, and alkyl difluoroacetate (IV), without additional solvent to form an enolate (V), b) releasing the corresponding alkyl 4,4-difluoroacetoacetate (I) from the enolate (V) by means of acid, c) removing the salt formed from cation M and acid anion as a solid and d) converting (I), without isolation from the crude reaction mixture, to the alkyl 2-alkoxymethylene-4,4-difluoro-3-oxobutyrate (VI), and the use of (VI) for preparing 1-methyl-3-difluoromethyl-pyrazol-3-ylcarboxyates (VII).