Synthesis of 2,3,5,6-tetrahydro-4H-1,4-thiazin-3-one 1,1-dioxides from methyl (styrylsulfonyl)acetate

Methyl (styrylsulfonyl)acetate ( 1 ) was shown to be a useful building block for the synthesis of 5-phenyl-2,3,5,6–4H-tetrahydro-1,4-thiazin-3-one (2), its 4-amino 3 , and 4-hydroxy 4 derivatives. Their 2-spirocyclopropanes 9, 10 , and 11 , and 2,7-diphenyl-6,7-dihydro-8H-pyrimido5,4-b]1,4]thiazinc 5,5-dioxide ( 18 ) were also prepared from 1 .