We report a photocatalyst-free radical hydrosilylation of alkenes enabled by direct visible-light excitation of chromophore-modified silyl radical precursors. By introducing a naphthalene chromophore into a 2-silyldihydroquinazolinone scaffold, a silyl radical is efficiently generated under visible-light irradiation without the assistance of transition metals or photoredox catalysis. This method enables hydrosilylation of various electron-deficient alkenes, providing the corresponding silylated products in moderate to good yields. Radical cyclization and Smiles rearrangement reactions were also achieved, highlighting the versatility of this transformation. Mechanistic studies indicated that the reaction was initiated by direct excitation of the silyl radical precursor to its triplet excited state, followed by homolytic C–Si bond cleavage, proceeding via a nonchain radical pathway.
Uchikura et al. (Thu,) studied this question.