Hydroxyl Radicals Unlock Strong C( <i>sp</i> <i> ³ </i> )─Si Bonds: Photocatalytic Alkylation and Silacycle Engineering

Abstract Organosilicon reagents play a significant role in the preparation of molecules essential to synthetic chemistry, materials science, and medicinal chemistry. However, selectively transforming strong C( sp 3 )─Si bonds in unactivated organosilicon reagents remains a significant challenge due to their high stability and low reactivity. Herein, we report that hydroxyl radical generated from water (H 2 O) can effectively drive the homolysis of strong C( sp 3 )─Si bonds, enabling radical alkylation with electron‐deficient alkenes. We reveal that H 2 O facilitates the generation of alkyl radicals, including tertiary, secondary, and primary radicals. Even the inert Et 4 Si can be activated and used in radical alkylation under our methodology. Moreover, we show that this strategy can be applied to the radical difunctionalization of silacycles, leading to the synthesis of organosilicon compounds not previously achievable through other methods. We anticipate that this approach will serve as a foundation for the development of more advanced radical reactions with unactivated organosilicon reagents, thereby facilitating the synthesis of a wide range of valuable molecules.