Combined photoredox/engineered P450 enzymatic direct dioxygen-functionalization of arylalkanes to chiral acyloins

Abstract

To date, the examples of difunctionalization of alkanes to directly incorporate two functional groups are very limited. In this study, we combined photoorgano redox catalysis and P450 biocatalysts to obtain dioxygen-functionalization of α/β-C–H bonds of arylalkanes in a straightforward manner. The synthesis of enantiomerically chiral acyloins through a one-pot two-step photoredox/P450-catalyzed cascade reaction is described. Two P450 mutants with stereocomplementary bio-oxidation were obtained using mutagenesis technology and were able to asymmetrically hydroxylate ketones to acyloins with excellent ee values, which were further proved to be efficient on a wide range of substrates. Moreover, a photoredox synthesis of ketones in situ was developed by the direct carbonylation of aromatic methyl C–H bonds and subsequently combined with the aerobic P450-biocatalytic enantioselective hydroxylation of intermediate ketones, thus providing a green and sustainable approach towards optically pure acyloins.