A catalyst-free approach for the generation of sulfonyl radicals from aryldiazonium tetrafluoroborates in the presence of DABCO⋅(SO2 )2 is realized. The combination of aryldiazonium tetrafluoroborates, DABCO⋅(SO2 )2 , and aryl propiolates affords 3-sulfonated coumarins in good to excellent yields. This tandem reaction process involves radical addition, spirocyclization, and 1,2-migration of esters. Additionally, the in situ diazotization of a number of anilines allows the directional synthesis of desired 3-sulfonated coumarins in a one-pot, two-step process.

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An enantioselective three-component radical reaction of quinolines or pyridines with enamides and a-bromo carbonyl compounds by dual photoredoxand chiral Brønsted acid catalysis is presented. Arange of valuable chiral g-aminoacid derivatives are accessible in high chemo-, regio-, and enantioselectivity from simple,readily available starting materials under mild reaction conditions.U sing the same strategy, the asymmetric synthesis of 1,2-diamine derivatives is also reported.

The coupling of aryldiazonium tetrafluoroborates, DABCO⋅(SO2)2, and hydrazines under metal-free conditions leads to the formation of aryl N-aminosulfonamides. The reaction proceeds smoothly at room temperature and shows broad functional-group tolerance. A radical process is proposed for this transformation.

A visible-light-initiated α-perfluoroalkyl-β-heteroarylation of various alkenes with perfluoroalkyl iodides and quinoxalin-2(1H)-ones is presented. This three-component radical cascade reaction allows an efficient synthesis of a range of perfluoroalkyl containing quinoxalin-2(1H)-one derivatives in moderate to excellent yields under mild conditions. Reactions proceed via acidic aminyl radicals that are readily deprotonated to give the corresponding radical anions able to sustain the radical chain as single electron transfer reducing reagents. Hence, the overall cascade classifies as an electron-catalyzed process.

A copper(i)-catalyzed three-component reaction of triethoxysilanes, DABCO·(SO2)2, and alkyl halides is reported. This transformation provides a facile route to sulfones under ligand-free conditions catalyzed by copper(i) oxide. The insertion of sulfur dioxide is efficient, and both triethoxyarylsilanes and triethoxyalkylsilanes are practicable during the coupling process.

A catalyst-free aminosulfonylation through insertion of sulfur dioxide with aryl/alkyl halides enabled by photoenergy is presented. Under ultraviolet irradiation, a three-component reaction of aryl/alkyl halides, sulfur dioxide, and hydrazines proceeds under mild conditions without any metals or photo-redox catalysts.

A copper-catalyzed aminosulfonylation of aryldiazonium tetrafluoroborates, DABCO·(SO), and N-chloroamines is described. This coupling reaction provides an efficient and simple approach to a wide range of sulfonamides in moderate to good yields under mild conditions. Mechanistic investigation suggests that a radical process and transition-metal catalysis are merged in this tandem reaction.