RING TRANSFORMATION OF 1,1-DIOXO-1,2-THIAZINE-6-CARBALDEHYDES WITH NITROGEN NUCLEOPHILES TO SUBSTITUTED PYRIDINE-3-SULFONANILIDES

1,1-Dioxo-1,2-thiazine-6-carbaldehydes 1 possessing a masked 1,5-dicar bonyl structure react with hydroxylamine with ring transformation to f orm the pyridine N-oxides 2. These can be deoxygenated with PCl3 to gi ve the corresponding pyridine-3-sulfonanilides 3, which are available by the reaction of 1 with ammonia as well. The ring transformation of 1 with methylamine, benzylamine and hydrazine produces N-substituted m esoionic pyridinium salts 6-8. The cyclohexane-fused thiazine-6-carbal dehyde 9 can be transformed with ammonia to the 5,6,7,8-tetrahydoquino line 10. Reaction of 2 with NaNO2/HCl enables the introduction of the nitro group into the anilide part of the molecule.