Transition metal-catalyzed hydroalkylations offer efficient routes to install alkyl fragments onto readily available olefins. However, the formation of quaternary carbon centers through olefin hydroalkylations with tertiary alkyl electrophiles remains a formidable synthetic challenge. Difficulty arises as a result of steric congestion, which slows the rate of oxidative addition and promotes deleterious β-hydride elimination. Here, we report a boron-mediated coupling strategy using nickel/photoredox dual catalysis that circumvents these limitations and enables anti-Markovnikov hydroalkylations of unactivated olefins with carboxylic acid derivatives as alkylating partners. Our protocol proceeds via initial hydroboration, followed by a sequence of deboronative and decarboxylative radical generation, radical sorting, and bimolecular homolytic substitution (SH2). This mild and practical approach allows the construction of densely substituted carbon frameworks, including sterically congested quaternary carbon centers, providing a solution to a long-standing challenge in fragment-coupling chemistry.
Zhang et al. (Fri,) studied this question.