A General Approach to 4-unsubstituted and 4-alkyl-substituted 5-acyl-1,2,3,4-tetrahydropyrimidine-2-thiones(ones) via α-(thio)ureidoalkylation of 1,3-diketones or β-oxoesters

A new general approach to a large variety of hitherto hardly accessible 4-unsubstituted and 4-alkyl-substituted 5-acyl-1,2,3,4-tetrahydropyrimidine-2-thiones(ones) has been developed. The approach is based on the reaction of enolates of various 1,3-diketones or β-oxoesters with readily available N -[alkyl(tosyl)methyl]thioureas, N -(azidomethyl)thiourea, and N -[alkyl(tosyl)methyl]ureas followed by TsOH-catalyzed dehydration of the intermediate 4-hydroxyhexahydropyrimidine-2-thiones(ones) without or with isolation of the latter.