Cobalt-catalyzed enantioselective hydroetherification of alkenes and symmetric 1,3-diketones

Abstract

Catalytic asymmetric hydroetherification of alkenes constitutes an efficient strategy toward enantioenriched oxygenated building blocks from readily available starting materials. However, the enantioselective intermolecular transformation of simple alkenes is particularly underdeveloped. Here, a Co(III)-hydride-mediated enantioselective olefin hydroetherification through radical-polar crossover H atom transfer has been described, with cyclic 1,3-diketone derivatives as O nucleophilic partners. This practical method is applicable for both styrenes and aliphatic alkenes with good functional group tolerance, enabling facile access to structurally diverse chiral vinylogous ester derivatives with excellent regio-, chemo-, and enantioselectivity. Theoretical studies have shown that the formation of alkyl Co(III) intermediates and the S_N2-substitution of alkyl Co(IV) with nucleophiles have an effect on the stereoselectivity of the products. Additionally, the O–H···π interaction between the –OH moiety of substrate moiety and salen ligand plays a crucial role in determining unique asymmetric C–O bond chemoselectivity compared to the disfavored steric hindrance in C–C bond construction.