Photoisomerization of sultams derived from saccharin; Part 3: Dihydro[1]benzothieno[3,2-b]pyrrole 4,4-dioxides from dihydropyrrolo[1,2-b][1,2]benzisothiazole 5,5-dioxides

1-Substituted 2,3-dihydropyrrolo[1,2-b][1,2]benzisothiazole 5,5-dioxides 7a -c,e undergo a smooth and efficient transformation into the 2,3-dihydro[1]b enzothieno[3,2-b]pyrrole 4,4-dioxides 8a-c,e upon irradiation at 254 nm in acetonitrile. The structures of the products have been elucidated by spectr oscopic methods and a single crystal X-ray structure determination for 8b.