1, 3-Oxazines and Related Compounds. VI. Synthesis and Some Reactions of 2, 6-Disubstituted 4H-1, 3-Thiazin-4-ones

Abstract

Various of 2, 6-disubstituted 4H-1, 3-thiazin-4-ones (5) were synthesized by successive treatment of N-acylacetylcarboxamides with acid (such as 70% perchloric acid or fluorosulfonic acid) and hydrogen sulfide. Reactions of 5 were investigated ; ammonolysis with ethanolic ammonia gave the corresponding pyrimidin-4-ones; hydrolysis of 2-alkyl-1, 3-thiazine derivatives yielded ring-opened N-acyl-β-mercaptocrotonamides ; reduction with NaBH₄ or LiAlH₄ afforded 3, 4-dihydro-2H-1, 3-thiazin-4-one derivatives.