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.