Dearomatization Silylation of Benzofurans and Furopyridines via Silyl Radical Addition and Endocyclic C–O Bond Scission

Abstract

Direct introduction of silyl radicals to forge C−Si bonds is of central importance in organic synthesis, owing to the formidable potential of silyl groups as coupling partners for further derivatization reactions to achieve more valuable compounds. Cleavage of heteroaromatic endocyclic carbon−heteroatom bonds to assemble C− Si bonds is scarce. Here, we demonstrate a dearomatization silylation of benzofurans and furopyridines via silyl radical addition and C(2)−O bond scission under metal-catalyst-free and mild conditions. Preliminary mechanistic experiments suggest that these transformations involve radical/single-electron transfer and [1,5]-Brook rearrangement processes. This protocol for the total synthesis of Doxepin and oxyresveratrol derivatives is carried out. The silylated products in several transformation reactions have proven to be useful as synthetic intermediates.