TY - JOUR

T1 - To Rebound or...Rebound? Evidence for the "alternative Rebound" mechanism in Câ'H Oxidations by the systems nonheme Mn Complex/H2O2/carboxylic acid

AU - Ottenbacher, Roman V.

AU - Bryliakova, Anna A.

AU - Shashkov, Mikhail V.

AU - Talsi, Evgenii P.

AU - Bryliakov, Konstantin P.

N1 - Funding Information: This work was supported by the Russian Science Foundation, project 20-13-00032 (for Novosibirsk State University). A.A.B. acknowledges the access to the supercomputer facilities of the Computing Centre of Novosibirsk State University. R.V.O., M.V.S., E.P.T., and K.P.B. gratefully acknowledge the access to the facilities of the shared research center “National center of investigation of catalysts”, provided by Boreskov Institute of Catalysis. Publisher Copyright: © 2021 American Chemical Society. All rights reserved.

PY - 2021/5/7

Y1 - 2021/5/7

N2 - In this work, it has been shown that aliphatic Câ'H oxidations by bioinspired catalyst systems Mn aminopyridine complex/H2O2/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 H2O2molecule, 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) [LMnV(O)OAc]2+active species followed by competitive OH/OC(O)R rebound. This mechanism has been unprecedented for Câ'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. copy; 2021 American Chemical Society.

AB - In this work, it has been shown that aliphatic Câ'H oxidations by bioinspired catalyst systems Mn aminopyridine complex/H2O2/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 H2O2molecule, 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) [LMnV(O)OAc]2+active species followed by competitive OH/OC(O)R rebound. This mechanism has been unprecedented for Câ'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. copy; 2021 American Chemical Society.

KW - Biomimetic catalysis

KW - Câ'H activation

KW - Hydrogen peroxide

KW - Manganese

KW - Mechanism

UR - http://www.scopus.com/inward/record.url?scp=85106399321&partnerID=8YFLogxK

U2 - 10.1021/acscatal.1c00811

DO - 10.1021/acscatal.1c00811

M3 - Article

AN - SCOPUS:85106399321

VL - 11

SP - 5517

EP - 5524

JO - ACS Catalysis

JF - ACS Catalysis

SN - 2155-5435

IS - 9

ER -