Process for producing 2- (aminomethylidene) -4,4-difluoro-3-oxobutyric acid ester

The present invention is a compound of formula (I) [Chemical 1] [Where R 1 , R 2 and R 3 are each independently of each other C 1 -C 6 -alkyl, C 1 -C 6 -haloalkyl, C 2 -C 6 -alkenyl, C 3 -C 10 -cycloalkyl or benzyl. Or NR 2 R 3 is a 5- to 10-membered heterocyclic group] 2- (aminomethylidene) -4,4-difluoro-3-oxobutyric acid ester, a process for the preparation of a compound of formula (I), wherein the corresponding 3-aminoacrylic acid ester is reacted with difluoroacetyl fluoride And the use of compounds of formula (I) in a process for the preparation of difluoromethyl-substituted pyrazol-4-ylcarboxylic acids and esters thereof. [Selection figure] None