Synthesis of oxasilolanes by TBAT-catalyzed hydroxyl-directed hydrosilylation

The reaction of allylic and homoallylic styrenyl alcohols with diphenylsilane and catalytic tetrabutylammonium difluorotriphenylsilicate (TBAT) produces 5- and 6-membered ring oxasilolanes respectively. Differing substitution at the carbinol position, phenyl ring, and carbon-carbon double bond were all found to have significant impacts on both yield and diastereoselectivity. A mechanism is proposed involving fluoride-promoted intramolecular hydrosilylation and formation of an intermediate benzylic anion, followed by cyclization and oxasilolane formation.