Photoredox-Catalyzed 1,4-Dichloromethyldimerization of Alkenes with Chloroform: Access to Polychlorinated Vicinal Diaryl Alkanes

A visible-light-mediated strategy is reported for the direct synthesis of polychlorinated vicinal diaryl alkanes from aryl alkenes and chloroform. In this approach, two haloalkyl radicals generated from chloroform via halogen atom transfer (XAT) and direct single electron transfer (SET) within the same photoredox catalysis cycle enable the 1,4-dichloromethyldimerization of alkenes. Besides chloroform, this strategy is applicable to carbon tetrachloride, bromotrichloromethane, and α-bromo carboxylic esters, yielding corresponding 1,4-disubstituted vicinal diaryl alkanes. Diverse polychlorinated structures containing highly congested vicinal quaternary carbon centers are effectively synthesized by this method. The potential of this reaction in late-stage drug modification is highlighted by the successful transformation of olefins with pharmaceutical structures.