UNEXPECTED DESULFONATION OF α-PHENYLSULFONYL ENAMINOACRYLATES DURING THEIR CYCLISATION TO NEW N-ARYL 4H-1,4-BENZOTHIAZINE-l,l-DIOXIDES

Abstract

Abstract An unexpected desulfonation of α-phenylsulfonyl-enaminoacrylates occurred during their cyclisation to novel 6,7-dichloro-N-aryl-4H-1,4-benzothiazine-1,1-dioxides using potassium carbonate and silver nitrate in DMF. This last cyclisation step was not completed in five hours of reaction but, instead of higher yields of the desired cyclic 4H-benzothiazines, a mixture of the above mentioned target compounds and desulfonated N-formyl-2-aryl-enanii-noacrylates were obtained.