Syntheses of oxazolecarboxylic acid derivatives. XV. Hydrogenolysis of aminoxazoles. (8). Mechanism of the hydrogenolysis of 2-aminoxazoles (author's transl)

Abstract

In confirmation of reduction intermediates, various 2-aminoxazoles (I) and 2-acetamidoxazoles (XIV) were submitted to catalytic reduction. In the hydrogenolysis of I, ring cleavage occurred in competition with the addition of hydrogen to the C (4)-C (5) double bond. When using palladium-carbon or platinum oxide catalyst, 4-phenyl-5-alkyl-I was mainly converted to alkylureas (IV) via (E)-alkenylureas (II), and 5-phenyl-I was converted to IV via II and 2-amino-2-oxazolines (III). When using platinum oxide catalyst, 4- or 5-alkyl-I was largely converted to IV via II. In both 4-phenyl-5-alkyl-I and alkyl-I, III was obtained as a by-product. The mechanism of the hydrogenolysis of I was also examined.