Yuanyuan An

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.

Vicinal Difunctionalization of Alkenes through A Multicomponent Reaction with the Insertion of Sulfur Dioxide

A four-component reaction of aryldiazonium tetrafluoroborates, sulfur dioxide, alkenes, and hydroxylamines under mild conditions is accomplished. No catalyst or additive is needed for the vicinal difunctionalization of alkenes with the insertion of sulfur dioxide. Not only DABCO⋅(SO2 )2 (DABCO=1,4-diazabicyclo[2.2.2]octane) but also potassium metabisulfite (K2 S2 O5 ) is effective in this transformation. The multicomponent reaction proceeds efficiently at room temperature with broad substrate scope, leading to the corresponding products in good yields.

A copper-catalyzed sulfonylative C–H bond functionalization from sulfur dioxide and aryldiazonium tetrafluoroborates

Sulfonylative C–H bond functionalization through a copper-catalyzed three-component reaction of 8-aminoquinoline amides, DABCO·(SO2)2 and aryldiazonium tetrafluoroborates is developed. Excellent selectivity in the para-position is observed for this copper-catalyzed transformation. This reaction is triggered by a copper-chelated complex via the coordination of the copper catalyst with the substrate and arylsulfonyl radical generated in situ, thus providing 5-sulfonyl-8-aminoquinoline amides in moderate to good yields.

Radical cyclization of benzene-tethered 1,7-enynes with aryldiazonium tetrafluoroborates: a facile route to benzo[j]phenanthridines

A radical cyclization of benzene-tethered 1,7-enynes with aryldiazonium tetrafluoroborates in the presence of copper(II) acetate and DABCO˙(SO2)2 is developed. This transformation is triggered by arylsulfonyl radicals which are generated in situ from aryldiazonium tetrafluoroborates and DABCO˙(SO2)2. This procedure is compatible with a wide range of functional groups, providing a facile route for the synthesis of diverse benzo[j]phenanthridines.

Synthesis of trifluoromethylated 3,4-dihydroquinolin-2(1H)-ones via a photo-induced radical cyclization of benzene-tethered 1,7-enynes with Togni reagent

A photoinduced radical cyclization of benzene-tethered 1,7-enynes with Togni reagent in the presence of sodium iodide is developed. Under ultraviolet irradiation, (Z)-4-(iodomethylene)-3-(2,2,2-trifluoroethyl)-3,4-dihydroquinolin-2(1H)-ones are generated in moderate to good yields. The transformation works well without any metals or photo-redox catalysts at room temperature. During the reaction process, the reaction proceeds through a trifluoromethyl radical-triggered α,β-conjugated addition/intramolecular 6-exo cyclization/iodination, with the formation of multiple bonds. Good functional group tolerance is observed under the reaction conditions.

A general route to fluorinated 3,3-disubstituted 2-oxindoles via a photoinduced radical cyclization of N-arylacrylamides under catalyst-free conditions

A catalyst-free radical cyclization of N-arylacrylamides with fluorinated alkyl iodides or the Togni reagent enabled by photoenergy is presented for the first time. Under ultraviolet irradiation, the generation of fluorinated 3,3-disubstituted 2-oxindoles proceeds smoothly without any metals or photoredox catalysts. The broad reaction scope is demonstrated with good functional group tolerance. During the process, fluorinated alkyl groups can be easily incorporated.