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.
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