Studies on Ketene and Its Derivatives. XXXIV. : Reaction of Diketene with Urethane and Acid Amides

Abstract

Reaction of diketene with urethan and acid amide was examined. Heating of urethan with excess of diketene results in the formation of N-acetoacetylurethan (III) and N-ethoxycarbonyl-2, 6-dimethyl-4-oxo-4H-pyran-3-carboxamide (IV). IV is also obtained by refluxing III and diketene in benzene, in the presence of triethylamine. Acetamide and benzamide react with diketene in acetic acid to form respectively N-acetoacetyl-acetamide (VI : R=CH₃) and N-acetoacetylbenzamide (VI : R=C₆H₅). Under the same condition, formamide and diketene form 3-acetyl-6-methyl-2, 4-pyridinedione (V) but the corresponding products were not isolated in the reaction with other acid amides.