Toward the synthesis of novel fluorinated building blocks: 3,4-difluorothiophene-1,1-dioxide

Addition of elemental fluorine to 2,5-dihydrothiophene-1,1-dioxide (4) prov ided a mixture of isomeric 3,4-difluoro-2,3,4, 5-tetrahydrothiophene-1,1-di oxides (5) in moderate yield. Photochemical chlorination of each of these i somers gave the same product mixture consisting mainly of trans-3-chloro-3, 4-difluoro-2,3,4,5-tetrahydrothiophene-1,1-dioxide (9a) and trans-3,4-dichl oro-3,4-difluoro-2,3,4,5-tetrahydrothiophene-1, 1-dioxide (11b). Dehydrohal ogenation of the former gave 3,4-difluoro-4,5-dihydrothiophene-1,1-dioxide (12) as the main product, whereas dehydrohalogenation of the latter gave 3, 4-difluorothiophene-1,1-dioxide (3) as the main product. (C) 1994 Elsevier Science S.A. All rights reserved.