A photoinduced vicinal difluoroalkylation and aminosulfonylation of alkynes under photocatalysis was realized. The combination of ethyl 2-bromo-2,2-difluoroacetate, alkynes, and DABCO⋅(SO ) 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.

A four-component reaction of terminal alkynes, aryldiazonium tetrafluoroborates, sulfur dioxide surrogate of DABCO⋅(SO ) , and potassium halide in the presence of copper(I) chloride (10 mol %) gives rise to β-halo vinylsulfones with good stereoselectivity. The vicinal difunctionalization of alkynes through sulfonylation and halogenation with the insertion of sulfur dioxide works efficiently. A plausible mechanism is proposed, which includes a radical process.

Direct vicinal difunctionalization of alkynes through a catalyst-free four-component reaction of Togni's reagent, alkynes, sulfur dioxide, and hydrazines at room temperature is developed, which generates (E)-3,3,3-trifluoroprop-1-ene-1-sulfonohydrazides in good yields.

Stereoselective vicinal difunctionalization of alkynes through trifluoromethylation and sulfonylation via a three‐component reaction of alkynes, sodium sulfinates, and Togni reagent under catalyst‐ and additive‐free conditions has been realized. This reaction proceeds at room temperature in dimethyl sulfoxide (DMSO), providing (E)‐β‐trifluoromethylvinyl sulfones in moderate to good yields. The advantages of this tandem radical process include extremely mild conditions, excellent stereoselectivity, and easy experimental operation.magnified image

Under visible light irradiation, 2-ethynylbenzenesulfonamides react with Togni's reagent in the presence of a photocatalyst leading to 3-(2,2,2-trifluoroethylidene)-2,3-dihydrobenzo[d]isothiazole 1,1-dioxides in good yields. This transformation proceeds efficiently at room temperature through a photo-initiated trifluoromethylation.