Enantioselective Benzylic Hydroxylation of Arylalkanes with H2O2 in Fluorinated Alcohols in the Presence of Chiral Mn Aminopyridine Complexes

Enantioselective Benzylic Hydroxylation of Arylalkanes with H2O2 in Fluorinated Alcohols in the Presence of Chiral Mn Aminopyridine Complexes Full article

Journal

ChemCatChem
ISSN: 1867-3880 , E-ISSN: 1867-3899

Output data

Year: 2018, Volume: 10, Number: 22, Pages: 5323-5330 Pages count : DOI: 10.1002/cctc.201801476

Tags

Asymmetric catalysis; C-H hydroxylation; enzyme models; hydrogen-bond donor; hydrogen peroxide; manganese

Authors

Ottenbacher Roman V. ^1,2 , Talsi Evgenii P. ^1,2 , Rybalova Tatyana V. ^1,3 , Bryliakov Konstantin P. ^1,2

Affiliations

1	(Данные Web of science) Novosibirsk State Univ, Novosibirsk 630090, Russia
2	(Данные Web of science) Boreskov Inst Catalysis, Novosibirsk 630090, Russia
3	(Данные Web of science) Vorozhtsov Novosibirsk Inst Organ Chem, Novosibirsk 630090, Russia

A series of chiral bioinspired Mn-aminopyridine complexes of the type [L*Mn-II(OTf)(2)] (where L* is 2,2 '-bipyrrolidine derived ligand, bearing trifluoroalkoxy and alkyl substituents) have been tested as catalysts in benzylic C-H hydroxylation of arylalkanes with H2O2 in fluorinated ethanols media. In 2,2,2-trifuoroethanol, the yield of the target ethylbenzene oxidation product, chiral 1-phenylethanol, reaches 45 %, which is much better than in the common solvent CH3CN (5-6 %). The selectivity for 1-phenylethanol formation increases in the following order: CH3CN<2-fluoroethanol<2,2-difluoroethanol<2,2,2-trifuoroethanol, while 2,2-difluoroethanol ensures the highest asymmetric induction in this series, affording chiral benzylic alcohols with up to 89 % ee. In trifluoroethanol, the observed primary k(H)/k(D) value of 2.3 has been measured for the oxidation of 1-phenylethanol/alpha-D-1-phenylethanol, which is similar to that in CH3CN (2.2). At the same time, depending on the solvent, CH3CN or 2,2,2-trifuoroethanol, the oxidations of 1-phenylethanol demonstrates drastically different linear free-energy relationships; possible effect of the hydrogen-bond donor (HBD) nature of CF3CH2OH is discussed in this context. Noticeably, it has been shown that by switching the absolute chirality ((S,S)- or (R,R)-) of the catalyst, the oxidation of complex substrate of natural origin, estrone acetate, can be diverted to predominant formation of either the tertiary C9-alcohol or of the C6-ketone, respectively.

Ottenbacher R.V. , Talsi E.P. , Rybalova T.V. , Bryliakov K.P.
Enantioselective Benzylic Hydroxylation of Arylalkanes with H2O2 in Fluorinated Alcohols in the Presence of Chiral Mn Aminopyridine Complexes
ChemCatChem. 2018. V.10. N22. P.5323-5330. DOI: 10.1002/cctc.201801476 WOS Scopus РИНЦ OpenAlex

Published online:	Nov 5, 2018
Published print:	Nov 22, 2018

Web of science:	WOS:000451444000027
Scopus:	2-s2.0-85056107536
Elibrary:	38669445
OpenAlex:	W2894655722

DB	Citing
Web of science	48
Scopus	46
Elibrary	49
OpenAlex	54