Photocatalytic Radical Alkylation of Electrophilic Olefins by Benzylic and Alkylic Zinc-Sulfinates

The decarboxylative coupling of carboxylic acids has numerous applications in photoredox catalysis.(1) In these reactions, monoelectronic oxidation of carboxylate anions, followed by carbon dioxide evolution from the so formed RCOO•, gave entry to nucleophilic radicals (R•) that were found to react with electrophilic alkenes.(2) An interesting alternative for the generation of radical species can be based on sulfinic acids or sulfinates,(3) with the advantage that the oxidation potentials of sulfinates are lower compared to carboxylate anions. A radical-based functionalization strategy that involves the use of sodium and zinc bis(alkylsulfinate) reagents has already been developed by Baran.(4) Herein we describe a new procedure to accomplish the difficult radical alkylation of electrophilic alkenes using benzylic and alkyl sufinates in combination with commercially available photo- catalysts and visible light irradiation. Moreover, it is shown that zinc sulfinates can be used for facile not-radical sulfonilation reactions with highly electrophilic Michael acceptors.