Iodobenzene-catalyzed preparation of 3,4-dihydro-1H-2,1-benzothiazine 2,2-dioxides from 2-Aryl-N-methoxyethanesulfonamides with m-chloroperoxybenzoic acid

Iodobenzene-catalyzed cyclization of 2-aryl-N-methoxyethanesulfonamides with m-chloroperoxybenzoic acid results in the corresponding 1-methoxy-3,4-dihydro-1H-2,1-benzothiazine 2,2-dioxides in moderate to good yields. In this reaction, reactive hypervalent iodine [(hydroxy)(tosyloxy)iodo] benzene, formed in situ, reacts with the 2 -aryl-N-methoxyethanesulfonamides in an electrophilic manner at the aromatic ring to give the corresponding 1-methoxy-3,4-dihydro-1H-2, 1-benzothiazine 2,2-dioxides.