Enantioselective Oxidation of Benzylic C–H Bonds via Dual Photoredox and Copper Catalysis

Directly asymmetric oxidation of C(sp3)–H bonds of organic molecules would radically alter current methods of synthesizing chiral alcohols and esters, which are widely existed in the structures of natural products, pharmaceuticals, and fine chemicals. The Kharasch–Sosnovsky reaction is commonly used process for oxidation of allylic C(sp3)–H bonds of alkenes to yield allyl esters. However, its asymmetric variant is limited to cycloalkenes, and the enantioselectivity and efficiency of the reactions of open-chain alkenes are low. Moreover, asymmetric Kharasch–Sosnovsky reactions of alkanes remain a seemingly insurmountable challenge. However, we herein report a method for highly enantioselective oxidation of benzylic C(sp3)–H bonds of arylalkanes by dual photoredox and copper catalysis. The method extends the scope of the Kharasch–Sosnovsky reaction to alkanes and, more importantly, uses alcohols or carboxylic acids instead of peroxides as oxygenated coupling partners. With this method, we obtained various chiral alcohols and esters with high enantioselectivity directly from readily available arylalkanes.