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In this work, it has been shown that aliphatic C−H oxidations by bioinspired catalyst systems Mn aminopyridine complex/H 2 O 2 /carboxylic acid in acetonitrile afford predominantly a mixture of the corresponding alcohol and the ester. The alcohol/ ester ratio is higher for catalysts bearing electron-donating groups at the aminopyridine core. Isotopic labeling studies witness that the oxygen atom of the alcohol originates from the H 2 O 2 molecule, while the ester oxygen comes exclusively from the acid. Oxidation of ethylbenzene in the presence of acetic acid affords enantiomerically enriched 1-phenylethanol and 1-phenyl acetate, with close enantioselectivities and the same sign of absolute chirality. Experimental data and density functional theory calculations provide evidence in favor of the rate-limiting benzylic H atom abstraction by the high-spin (S = 1) [LMn V (O)OAc] 2+ active species followed by competitive OH/OC(O)R rebound. This mechanism has been unprecedented for C−H oxidations catalyzed by bioinspired Mn complexes. The trends governing the alcohol/ester ratios have been rationalized in terms of steric properties of the catalyst, acid, and substrate.

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