Selective Activation of C−H Bonds in a Cascade Process Combining Photochemistry and Biocatalysis

Selective oxyfunctionalizations of inert C−H bonds can be achieved under mild conditions by using peroxygenases. This approach, however, suffers from the poor robustness of these enzymes in the presence of hydrogen peroxide as the stoichiometric oxidant. Herein, we demonstrate that inorganic photocatalysts such as gold–titanium dioxide efficiently provide H2O2 through the methanol‐driven reductive activation of ambient oxygen in amounts that ensure that the enzyme remains highly active and stable. Using this approach, the stereoselective hydroxylation of ethylbenzene to (R)‐1‐phenylethanol was achieved with high enantioselectivity (>98 % ee) and excellent turnover numbers for the biocatalyst (>71 000).F.H and W.Z. gratefully acknowledge financial support by the European Research Council (ERC Consolidator Grant No. 648026). B.O.B. and J.Z.B. are grateful for financial support from the German Research Foundation (DFG, Grant No. BL 1425/1‐1). We thank Ben Norder (Delft University of Technology) for XRD, Dr. Wiel H. Evers (Delft University of Technology) for TEM, and Prof. Fred Hagen (Delft University of Technology) for EPR measurements.Peer reviewe