Combined Electrooxidation and Proline Catalysis for Asymmetric Formal Cross-Dehydrogenative Coupling of Benzylic Alcohols with Ketones

Abstract

This article presents a method for asymmetric formal cross-dehydrogenative coupling of benzylic alcohols with ketones through combined electrooxidation and organocatalysis. Employing inexpensive and environmentally friendly proline as a chiral organocatalyst, various benzylic alcohols and simple ketones serve as substrates to directly obtain diverse chiral β-hydroxycarbonyl compounds with moderate to good yields (up to 85%) and excellent stereoselectivity (up to 99% ee and 99:1 dr). The reaction proceeds under mild conditions at room temperature in air, without oxidants or additives, demonstrating robust functional group tolerance and atom efficiency. Hydrogen gas released at the cathode is the sole byproduct. Using L- or D-proline allows straightforward access to both chiral configurations of β-hydroxycarbonyl compounds.