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.