Regioselective Synthesis of Alcohols by Catalytic Transfer Hydrogenation of Epoxides.

Reductive ring opening of readily available epoxides provides easy access to synthetically important alcohols. However, controlling the regioselectivity of the reaction under user-friendly conditions remains challenging. Here, we present an efficient methodology for regioselective transfer hydrogenation (TH) of epoxides to synthesize Markovnikov and anti-Markovnikov alcohols using 2-propanol as the hydrogen source. An [IrCl(cod)(NHC)] (cod = 1,5-cyclooctadiene, NHC = N-heterocyclic carbene) complex as a precatalyst enables the formation of secondary and tertiary alcohols in good to excellent yields via selective TH of mono- and 2,2-disubstituted terminal epoxides. Remarkably, we found that an NHC-Ir & Pd/C cooperative catalysis approach can steer the regioselectivity of the reaction to afford anti-Markovnikov alcohols. This cooperative catalysis approach enables the transfer hydrogenative ring opening of mono- and 2,2-disubstituted terminal aryl epoxides to form linear alcohols and challenging internal epoxides to give branched alcohols.