Danqing Zheng

Metal-free aminosulfonylation of aryldiazonium tetrafluoroborates with DABCO⋅(SO2)2 and hydrazines.

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.

Generation of Sulfonyl Radicals from Aryldiazonium Tetrafluoroborates and Sulfur Dioxide: The Synthesis of 3-Sulfonated Coumarins.

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.

A copper( i )-catalyzed three-component reaction of triethoxysilanes, sulfur dioxide, and alkyl halides

A copper(I)-catalyzed three-component reaction of triethoxysilanes, DABCO·(SO2)2, and alkyl halides is reported for the first time. This transformation provides a convenient and 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 plausible mechanism is proposed, supported by theoretical calculations.

Generation of N-aminosulfonamides via a photo-induced fixation of sulfur dioxide into aryl/alkyl halides

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 smoothly under mild conditions without any metals or photo-redox catalysts. The corresponding N-aminosulfonamides are afforded in good to excellent yields. A broad reaction scope is demonstrated with good functional group tolerance. Not only aryl bromide but also aryl chloride is suitable under the conditions. Additionally, alkyl halides are good substrates as well during the insertion of sulfur dioxide. A possible mechanism involving a radical process is proposed, supported by theoretical calculations.

Synthesis of 3-((arylsulfonyl)methyl)indolin-2-ones via insertion of sulfur dioxide using anilines as the aryl source

Facile assembly of 3-((arylsulfonyl)methyl)indolin-2-ones via insertion of sulfur dioxide starting from anilines, N-arylacrylamides and DABCO·(SO2)2 is developed. This one-pot reaction proceeds efficiently in dichloroethane, leading to sulfonated oxindoles in good yields. Anilines serve as the aryl source, and the in situ generated sulfonyl radicals from sulfur dioxide as the key intermediates are trapped by N-arylacrylamides to provide the corresponding products. Additionally, a broad reaction scope is observed under mild conditions.

An Efficient Route to Tetrahydroindeno[2,1-b]pyrroles via a Base-Promoted Reaction of (E)-2-Alkynylphenylchalcone with 2-Isocyanoacetate

A base-promoted cascade reaction of (E)-2-alkynylphenylchalcone with 2-isocyanoacetate provides a novel and efficient route for the synthesis of tetrahydroindeno[2,1-b]pyrroles. The reaction proceeds smoothly in air under mild conditions with high efficiency.

Synthesis of 3-(((2,3-dihydrobenzofuran-3-yl)methyl)sulfonyl) coumarins through the reaction of 2-(allyloxy)anilines, sulfur dioxide, and aryl propiolates

A facile route to 3-((2,3-dihydrobenzofuran-3-yl)methyl)sulfonyl coumarins through the reaction of 2-(allyloxy)anilines, DABCO-bis(sulfur dioxide), and aryl propiolates is achieved. During the reaction process, a 2-(allyloxy)aryl radical would be generated in situ, which would undergo the intramolecular addition of a double bond to afford an alkyl radical intermediate. Further insertion of sulfur dioxide would produce an alkylsulfonyl radical. The subsequent combination with aryl propiolates would provide sulfonyl-bridged dihydrobenzofuran and coumarin derivatives through radical cyclization and rearrangement.