Novel method for the synthesis of 3-acyl-1,6-dialkyl-7-methyl-1,6-naphthyridine-2,5(1H,6H)-diones (2) was developed. The reaction of 2-acyl-1-alkylamino-1-ethoxyethylenes (1) with acetyl chloride or β-keto amide 3 with acetyl chloride in the presence of p-toluenesulfonic acid gave 2 in moderate yield (14-59% yield).
alpha-Oxoketene O,N-acetals were prepared from beta-oxothiono esters and primary amines in the presence of triethylamine at room temperature within several hours in good yields.