Process for the production of [2-acetoacetyl-aminothiazolyl-(4)-]-acetic acid ethyl ester

The process for the production of [2-acetoacetylaminothiazolyl-(4)-]-acetic acid ethyl ester which comprises reacting [2-aminothiazolyl-(4)-]-acetic acid ethyl ester with diketene in an organic solvent in the presence of 5 to 15 percent of glacial acetic acid, based on the amount of said solvent, at a temperature between 30.degree. and 80.degree. C., said solvent being selected from the group consisting of an alkyl acetate having 1 to 4 carbon atoms in the alkyl group, an aromatic hydrocarbon, a halogenated hydrocarbon having 1 to 4 carbon atoms, amyl acetate, isopropyl cyclopentane, ethyl cyclopentane and propyl cyclopentane.