Bioinspired oxidations of aliphatic C–H groups with H2O2 in the presence of manganese complexes

Talsi, Evgenii P.; Ottenbacher, Roman V.; Bryliakov, Konstantin P.

doi:10.1016/j.jorganchem.2014.12.014

Cited by 35 publications

(15 citation statements)

References 56 publications

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“…One of the major trends has been the design of bioinspired transition‐metal (mostly Fe‐based) catalysts, capable of conducting the C−H oxygenation with environmentally benign oxidants, that is, H 2 O 2 and O 2 . In the last few years, we have shown that Mn–aminopyridine complexes with C 2 ‐symmetric bipyrrolidine‐derived ligands efficiently oxidize unactivated C−H groups in alkanes with H 2 O 2 , and studied the C−H hydroxylation mechanism ,. The Mn‐based catalysts have exhibited very good efficiencies (up to 1000 turnover numbers (TN)), many times higher than for the structurally similar Fe complexes…”

Section: Introductionmentioning

confidence: 74%

Asymmetric Autoamplification in the Oxidative Kinetic Resolution of Secondary Benzylic Alcohols Catalyzed by Manganese Complexes

2017

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Herein, chiral Mn–aminopyridine complexes have been shown to catalyze the oxidation of alkylarenes to enantiomerically enriched 1‐arylalkanols with hydrogen peroxide. The observed enantiomeric excess values result from the direct enantioselective benzylic C−H hydroxylation, accompanied by stereoconvergent oxidative kinetic resolution of the resulting alcohol. Testing several (S,S)‐bipyrrolidine derived Mn complexes has revealed a novel catalyst (6) that exhibits the best kinetic resolution in the series (krel up to 8.8), along with sufficient reactivity and efficiency (>1000 catalytic turnovers). The mechanistic study of the Mn‐mediated alcohol oxidation witnesses electrophilic active species (ρ=−1.2), with rate‐limiting H abstraction (kH/kD=2.2), followed by oxygen rebound and dehydration of the resulting gem‐diol to form the ketone. Intriguingly, while for the resolution of the relatively bulky 1,2‐diphenylethanol, krel is virtually constant throughout the reaction, for less bulky alcohols, krel increases with increasing conversion, in line with the rising optical purity of the 1‐arylalkanol. The latter participates in the oxidation as an auxiliary ligand, assisting the chiral recognition. This effect is related to the previously described asymmetric autocatalysis and asymmetric autoinduction, but is not identical with either of those, with the differences being discussed. To unambiguously identify this effect, the term asymmetric autoamplification (chiral autoamplification) is proposed.

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Section: Introductionmentioning

confidence: 74%

Asymmetric Autoamplification in the Oxidative Kinetic Resolution of Secondary Benzylic Alcohols Catalyzed by Manganese Complexes

2017

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“…The authors confirmed the electrophilic nature of the active oxidizing species. The latter demonstrated high 3˝/2˝ratios (40)(41)(42)(43)(44)(45)(46)(47)(48)(49), alcohol/ketone ratios > 5, and high stereospecificity in the oxidation of cis-1,2-dimethylcyclohexane [187]; kinetic studies revealed a sizable kinetic isotopic effect (k H /k D 4.5-4.7), indicating that that the H atom lies on the reaction coordinate and participates in the C-H bond breaking step. Altogether, the experimental data provided indirect evidence in favor of the participation of a high-valent (presumably oxometal(V) [188]) species, ruling out the contribution of a free-radical-driven oxidation pathway.…”

Section: New Types Of Ligands and Catalystsmentioning

confidence: 99%

New Trends in Oxidative Functionalization of Carbon–Hydrogen Bonds: A Review

Shul’pin

2016

Catalysts

174

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This review describes new reactions catalyzed by recently discovered types of metal complexes and catalytic systems (catalyst + co-catalyst). Works of recent years (mainly 2010-2016) devoted to the oxygenations of saturated, aromatic hydrocarbons and other carbon-hydrogen compounds are surveyed. Both soluble metal complexes and solid metal compounds catalyze such transformations. Molecular oxygen, hydrogen peroxide, alkyl peroxides, and peroxy acids were used in these reactions as oxidants.

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“…to the acetonitrile:dichloromethane solution of cyclohexane, catalyst 2 (2.5 mol %), and imidazole as additive (60 mol %), led to the formation of cyclohexanol and cyclohexanone (Table 1, entry 1) [50]. The 3:1 cyclohexanol:cyclohexanone ratio, the high (11.5) 3 • :2 • adamantane oxidation selectivity, the absence of effect of dioxygen on the oxidation outcome, and selective (non-statistical) oxygenation of heptane were indicative of a metal-mediated rather than radical-driven oxidation mechanism [51]. The authors hypothesized that the oxidation could be performed by the Mn V =O intermediate, the role of imidazole consisting in promoting the heterolytic cleavage of the O-O bond, to form the manganese-oxo species [52].…”

Section: C-h Oxidations With H 2 O 2 In the Presence Of Mn Porphyrinsmentioning

confidence: 98%

“…The authors hypothesized that the oxidation could be performed by the Mn V =O intermediate, the role of imidazole consisting in promoting the heterolytic cleavage of the O-O bond, to form the manganese-oxo species [52]. of heptane were indicative of a metal-mediated rather than radical-driven oxidation mechanism [51]. The authors hypothesized that the oxidation could be performed by the Mn V =O intermediate, the role of imidazole consisting in promoting the heterolytic cleavage of the O-O bond, to form the manganese-oxo species [52].…”

Section: C-h Oxidations With H 2 O 2 In the Presence Of Mn Porphyrinsmentioning

confidence: 99%

Direct Selective Oxidative Functionalization of C–H Bonds with H2O2: Mn-Aminopyridine Complexes Challenge the Dominance of Non-Heme Fe Catalysts

2016

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Non-heme iron(II) complexes are widespread synthetic enzyme models, capable of conducting selective C-H oxidation with H 2 O 2 in the presence of carboxylic acid additives. In the last years, structurally similar manganese(II) complexes have been shown to catalyze C-H oxidation with similarly high selectivity, and with much higher efficiency. In this mini-review, recent catalytic and mechanistic data on the selective C-H oxygenations with H 2 O 2 in the presence of manganese complexes are overviewed. A distinctive feature of catalyst systems of the type Mn complex/H 2 O 2 /carboxylic is the existence of two alternative reaction pathways (as found for the oxidation of cumenes), one leading to the formation of alcohol, and the other to ester. The mechanisms of formation of the alcohol and the ester are briefly discussed.

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Bioinspired oxidations of aliphatic C–H groups with H2O2 in the presence of manganese complexes

Cited by 35 publications

References 56 publications

Asymmetric Autoamplification in the Oxidative Kinetic Resolution of Secondary Benzylic Alcohols Catalyzed by Manganese Complexes

Asymmetric Autoamplification in the Oxidative Kinetic Resolution of Secondary Benzylic Alcohols Catalyzed by Manganese Complexes

New Trends in Oxidative Functionalization of Carbon–Hydrogen Bonds: A Review

Direct Selective Oxidative Functionalization of C–H Bonds with H2O2: Mn-Aminopyridine Complexes Challenge the Dominance of Non-Heme Fe Catalysts

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