Mechanistic Studies of Hydride Transfer to Imines from a Highly Active and Chemoselective Manganate Catalyst

Journal of the American Chemical Society, Journal Year: 2019, Volume and Issue: 141(29), P. 11677 - 11685

Published: June 28, 2019

We introduce a highly active and chemoselective manganese catalyst for the hydrogenation of imines. The has large scope, can reduce aldimines ketimines, tolerates variety functional groups, among them sensitive examples such as an olefin, ketone, nitriles, nitro aryl iodo substituent or benzyl ether. could investigate transfer step between imines hydride complex in detail. found that double deprotonation ligand is essential excess base does not lead to higher rate step. identified actual K–Mn-bimetallic species obtain structure K–Mn formed after by X-ray analysis. NMR experiments indicate well-defined reaction, which first order imine, bimetallic (K–Mn) hydride, independent from concentration potassium base. propose outer-sphere mechanism protons do seem be involved rate-determining step, leading transiently negatively charged nitrogen atom substrate reacts rapidly with HOtBu (2-methylpropan-2-ol) produce amine. This based on several observations, no dependency reaction concentration, observable amide complex, high constant conducted Hammett study. Furthermore, hydrogen catalytic cycle was experimentally probed monitored subsequent quantitative regeneration H2.

Language: Английский

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Manganese‐Catalyzed Asymmetric Hydrogenation of Quinolines Enabled by π–π Interaction**

Angewandte Chemie International Edition, Journal Year: 2020, Volume and Issue: 60(10), P. 5108 - 5113

Published: Nov. 26, 2020

Abstract The non‐noble metal‐catalyzed asymmetric hydrogenation of N‐heteroaromatics, quinolines, is reported. A new chiral pincer manganese catalyst showed outstanding catalytic activity in the affording high yields and enantioselectivities (up to 97 % ee). turnover number 3840 was reached at a low loading (S/C=4000), which competitive with most effective noble metal catalysts for this reaction. precise regulation enantioselectivity were ensured by π–π interaction.

Language: Английский

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Ligand-Controlled Copper(I)-Catalyzed Cross-Coupling of Secondary and Primary Alcohols to α-Alkylated Ketones, Pyridines, and Quinolines

Organic Letters, Journal Year: 2018, Volume and Issue: 20(3), P. 608 - 611

Published: Jan. 16, 2018

One hexanuclear Cu(I) cluster of 4,6-dimethylpyrimidine-2-thiolate efficiently catalyzes the dehydrogenative cross-coupling secondary and primary alcohols to α-alkylated ketones with high selectivity. This transformation proceeds through a one-pot sequence dehydrogenation alcohols, condensation aldehydes ketones, hydrogenation resulting α,β-unsaturated generate ketones. catalytic system also displays activity for annulation reaction γ-amino- 2-aminobenzyl yield pyridines quinolines, respectively.

Language: Английский

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Unmasking the Ligand Effect in Manganese-Catalyzed Hydrogenation: Mechanistic Insight and Catalytic Application

Journal of the American Chemical Society, Journal Year: 2019, Volume and Issue: 141(43), P. 17337 - 17349

Published: Oct. 21, 2019

Manganese-catalyzed hydrogenation reactions have attracted broad interest since the first report in 2016. Among reported catalytic systems, Mn catalysts supported by tridentate PNP- and NNP-pincer ligands most commonly been used. For example, a number of PNP-Mn pincer for aldehydes, aldimines, ketones, nitriles, esters. Furthermore, various NNP-Mn shown to be active less-reactive substrates such as amides, carbonates, carbamates, urea derivations. These observations indicated that exhibit higher reactivity than their PNP counterparts. Such ligand effect Mn-catalyzed has yet confirmed. Herein, we investigated origin applicability this effect. A combination experimental theoretical investigations showed on complexes were more electron-rich less sterically hindered counterparts, leading series reactions. Inspired hydrogenations, developed N-heterocycles. Specifically, hydrogenated N-heterocycles (32 examples) with up 99% yields, corresponding afforded low under same conditions. This verified is generally applicable both carbonyl noncarbonyl based catalysis.

Language: Английский

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Catalytic Hydrogenation of Cyclic Carbonates using Manganese Complexes

Angewandte Chemie International Edition, Journal Year: 2018, Volume and Issue: 57(41), P. 13449 - 13453

Published: Aug. 22, 2018

Catalytic hydrogenation of cyclic carbonates to diols and methanol was achieved using a molecular catalyst based on earth-abundant manganese. The complex [Mn(CO)

Language: Английский

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