Reductive Amination and Enantioselective Amine Synthesis by Photoredox Catalysis

Abstract

Photochemistry usually functions on a one‐photon‐one‐electron basis, leading to unstable radical intermediates that must be intercepted rapidly to allow efficient product formation. This can render multi‐electron reductions and enantioselective reactions particularly challenging. In this minireview, we discuss recent advances in the area of photo‐driven multi‐electron transfer with a particular focus on our own work on reductive amination and the enantioselective synthesis of amines by combined photoredox and enzyme catalysis. Polarity‐matched hydrogen atom transfer (HAT) between photochemically‐generated α‐amino alkyl radicals and thiols is a key step in these reactions. A cyclic reaction network comprised of light‐driven imine reduction by an Ir‐photocatalyst and enantioselective amine oxidation by the enzyme monoamine oxidase (MAO‐N‐9) was used to obtain enantioenriched amines from imines.