Hydroalkylation of Vinylarenes by Transition‐Metal‐Free In Situ Generation of Benzylic Nucleophiles Using Tetramethyldisiloxane and Potassium tert‐Butoxide

Hydrosilanes and Lewis bases are known to promote various reductive defunctionalizations, rearrangements, and silylation reactions, facilitated by enigmatic silicon/Lewis base-derived reactive intermediates. Despite the wide variety of transformations enabled by this reagent combination, no examples of intermolecular C(sp3)-C(sp3) forming reactions have been reported. In this work, we've identified 1,1,3,3-tetramethyldisiloxane (TMDSO) and KOtBu as a unique reagent combination capable of generating benzylic nucleophiles in-situ from styrene derivatives, which can subsequently react with alkyl halides to give a new C(sp3)-C(sp3) linkage via formal hydroalkylation. Mechanistic experiments suggest that the reaction proceeds through a key hydrogen atom transfer (HAT) step from a hydrosilane reducing agent to styrene, affording a benzylic radical that undergoes reductive radical polar crossover (RRPC) and subsequent SN2 alkylation.