Vicinal Difluoroalkylation and Aminosulfonylation of Alkynes under Photoinduced Conditions

A photoinduced vicinal difluoroalkylation and aminosulfonylation of alkynes under photocatalysis was realized. The combination of ethyl 2-bromo-2,2-difluoroacetate, alkynes, and DABCO center dot(SO2)(2) with hydrazines, catalyzed by 9-mes-10-methyl acridinium perchlorate in the presence of visible light, afforded (E)-ethyl 2,2-difluoro-4-aryl- 4-sulfamoylbut-3-enoates in good yields with high stereoselectivity. This four-component reaction proceeds through radical addition with the insertion of sulfur dioxide.