LAUSR

Bioinspired chiral Mn‐aminopyridine complexes [(S,S)‐LMnII(OTf)2] and [(R,R)‐LMnII(OTf)2] (where (S,S)‐L=(2S,2′S)‐1,1′‐bis((3‐methyl‐4‐(2,2,2‐trifluoroethoxy)pyridin‐2‐yl)methyl)‐2,2′‐bipyrrolidine, and (R,R)‐L=(2R,2′R)‐1,1′‐bis((3‐methyl‐4‐(2,2,2‐trifluoroethoxy)pyridin‐2‐yl)methyl)‐2,2′‐bipyrrolidine) have been shown to efficiently catalyze the benzylic C−H oxidation of arylalkanes with hydrogen peroxide in the presence of carboxylic acid additives, affording enantiomerically enriched 1‐arylalkanols and the corresponding ketones. Optically pure additive N‐Boc‐(L)‐proline, in combination with [(R,R)‐LMnII(OTf)2] complex, affords 1‐arylalkanols in up to 86 % ee, which is the highest reported enantioselectivity for direct benzylic hydroxylations with H2O2 in the presence of transition‐metal catalysts. Oxidative kinetic resolution only slightly contributes to the increase of the observed enantiomeric excess over the reaction course. The observed kH/kD values (3.5–3.6 for the oxidation of ethylbenzene/d10‐ethylbenzene) and competitive oxidation data are consistent with either a hydrogen‐atom transfer/oxygen rebound or hydride transfer/oxygen rebound asymmetric hydroxylation mechanism.