Iridium-Catalyzed Regioselective Silylation of Secondary Alkyl C–H Bonds for the Synthesis of 1,3-Diols

We report Ir-catalyzed intramolecular silylation of secondary alkyl C-H bonds. (Hydrido)silyl ethers, generated in situ by dehydrogenative coupling of a tertiary or conformationally restricted secondary alcohol with diethylsilane, undergo regioselective silylation at a secondary C-H bond γ to the hydroxyl group. Oxidation of the resulting oxasilolanes in the same vessel generates 1,3-diols. This method provides a strategy to synthesize 1,3-diols through a hydroxyl-directed, functionalization of secondary alkyl C-H bonds. Mechanistic studies suggest that the C-H bond cleavage is the turnover-limiting step of the catalytic cycle. This silylation of secondary C-H bonds is only 40-50 times slower than the analogous silylation of primary C-H bonds.