Process for the manufacture of acetoacetic acid methyl ester and acetoacetic acid ethyl ester

摘要

Methyl and ethyl esters of acetoacetic acid are made by reacting diketene, which may contain acetic acid and/or its anhydride, with methanol or ethanol in the presence, as catalyst, of at least one tertiary amine of the formula R1R2NZ wherein R1 and R2 are the same or different C1- 3 alkyl groups or together with a carbon, oxygen or nitrogen atom form a 5- or 6-membered ring, and Z is an alkyl, cycloalkyl or alkenyl group of at least 8 carbon atoms or the radical -(CH2)n-X, where n is 2 or more and X is a hydroxyl or mercapto group or an amino group which may be substituted. It is preferred to use the catalyst in amount of 0.3-10.0% by weight of alcohol. Suitable catalysts are those whose boiling points are at least 20 DEG C. above those of the esters in order that the reaction mixture can be distilled to obtain the esters overhead, leaving the catalyst as a residue. Catalysts used in the examples are (1) dimethylstearylamine, (2) dimethylaminoethanol and (3) N,N,N1,N1-tetramethylhexamethylene diamine.