ALKOXIDE-INDUCED REACTIONS OF N-SUBSTITUTED SACCHARINS - SYNTHESIS OF 1,2-BENZOTHIAZOCINE 1,1-DIOXIDE AND 2,3-DIHYDROPYRROLO[1,2-B]-[1,2]BENZISOTHIAZOLE 5,5-DIOXIDE DERIVATIVES

The reactions of saccharin derivatives 1 with sodium alkoxides were studied. Under mild conditions, compounds 1a-f gave the corresponding open sulfonamides 5a-f. Under drastic conditions, beta-(saccharin-2)propionic acid derivatives 1a,b reacted with sodium ethoxide affording saccharin and beta-ethoxypropionic acid derivatives 4a,b, gamma-(Saccharin-2)butyric acid derivatives 1c,d and gamma-(saccharin-2)-butyrophenone 1f reacted with sodium t-butoxide in dimethyl sulfoxide affording 5-substituted 6-hydroxy-3,4-dihydro-2H-1,2-benzothiazocine 1,1-dioxides 9. From mother liquors, 1-substituted 2,3-dihydropyrrolo[1,2-b][1,2]benzisothiazole 5,5-dioxides 10 were isolated several hours later, though not detected immediately after completing the reaction. When the reactions were carried out in t-butyl alcohol, the yields of 9 diminished and those of 10 increased with product ratio inversion. Different experimental observations on the possible pathway generating 9 and 10 are discussed.