Method for producing 3-amino-4,4,4-trifluorocrotonic acid esters

A process is described for preparing 3-amino-4,4,4-trifluorocrotonic esters of the formula (I) or the E/Z isomers or tautomeric forms thereof where R1 and R2 are each independently hydrogen, an optionally substituted linear C1-C4-alkyl radical or an optionally substituted benzyl radical and R3 is methyl or ethyl, which comprises a) reacting an alkyl trifluoroacetate with an alkyl acetate of the formula CH3-CO-OR3 and an alkali metal alkoxide to give an enolate of a trifluoroacetoacetic ester of the formula (II) where M is sodium or potassium and R3 is as defined above, and subsequently b) allowing the alkali metal enolate of the trifluoroacetoacetic ester from stage a) to react without further purification directly with an amine of the formula NHR1R2 in the presence of an acid to give the 3-amino-4,4,4-trifluorocrotonic ester. With the aid of this two-stage process, the 3-amino-4,4,4-trifluorocrotonic esters can be prepared in high yields without significant by-products.