Heterocyclic studies. Part XXXIV. Some 5H-pyrimido[4,5-b][1,4]thiazine-6(7H)-ones, -4,6(3H,7H)-diones and -2,4,6(1H,3H,7H)-triones

Abstract

Condensation of several 6-substituted 5-aminopyrimidine-4(3H)-thiones (1; X = Cl, OEt, SH, or OMe) with chloroacetic acid and of the methoxy-compound with various α-bromo-esters gave corresponding 4-substituted 5H-pyrimido[4,5-b][1,4]thiazin-6(7H)-ones. The 4,6(3H,7H)-diones were made by acidic hydrolysis of the corresponding 4-methoxy-6(7H)-ones. Alkylation before or both before and after hydrolysis furnished 5- or 3,5-dialkyl derivatives of the diones. 3-Methyl- and 1,3-dimethyl-5H-pyrimido[4,5-b][1,4]thiazine-2,4,6(1H,3H,7H)-trione were made from the appropriate pyrimidinethiones and chloroacetic acid.