Ketene-S,S-acetals-V: the reactions of α-keto and α-cyanoketene-S,S-acetals with guanidine and thiourea: a new general synthesis of alkoxy-pyrimidines

Abstract

The ketoketene-S,S-acetals (5a-c) react with guanidine and thiourea in the presence of alcoholic sodium alkoxides to give 2-amino- and 2-mercapto-4-alkoxy-5-aryl-6-methyl-pyridimidines (6a-k) respectively in good yields. The α-cyanoketene-S,S-acetals (9a-d) similarily gave 5-substituted-2,4-diamino-6-alkoxy-pyridimidines (10a-e) with guanidine in 50-60% overall yields. The unexchanged 2,4-diamino-5-p-chlorophenyl-6-methylthio-pyrimidine (11) was prepared from 9c as a typical example using identifical conditions described for 7. The synthesis of 5,6-fused pyrimidines (14a-f), (19) and (23a-e) was also accomplished using the cyclic ketene-S,S-acetals (13a-c) and (22a-b). The present method is found to be more convenient and efficient than reported methods for alkoxy and methylthiopyrimidines.