Hydroalkylation of styrenes enabled by boryl radical mediated halogen atom transfer

Organohalides are a class of widely accessible synthetic synthons, but their high reduction potential has hampered their use in radical chemistry. However, recent advances in photoredox-catalyzed halogen atom transfer (XAT) strategies have introduced milder and more straightforward methods to achieve radical formation. In this work, we present a ligated boryl radical-mediated halogen abstraction from alkyl and aryl bromides, thus generating C-centered radicals. The generated radicals were further engaged in the anti-Markovnikov hydroalkylation of electronically diverse styrenes. The methodology proved to be applicable to the generation of (1o, 2o, 3o) alkyl radicals as well as aryl radicals, demonstrating high tolerance and robustness. The role of the ligated boryl radical in enabling hydrogen atom transfer (HAT) from H2O was elucidated as well. Mechanistic investigations and density functional theory (DFT) calculations were performed to enlighten the overall reaction pathway.