Recent advances in homogeneous base-metal-catalyzed transfer hydrogenation reactions

Baidilov, Daler; Hayrapetyan, Davit; Khalimon, Andrey Y.

doi:10.1016/j.tet.2021.132435

Cited by 41 publications

(24 citation statements)

References 156 publications

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“…Transition metal hydrides are crucial intermediates in a plethora of catalytic reactions, including reactions relevant to (i) energy storage applications, (ii) the synthesis of pharmaceuticals, − and (iii) the preparation of monomers for polymerization . In many of these reactions, hydride transfer (either from a transition metal hydride to a substrate or from a substrate to a transition metal to form a transition metal hydride) is the turnover-limiting step.…”

Section: Introductionmentioning

confidence: 99%

Correlating Thermodynamic and Kinetic Hydricities of Rhenium Hydrides

et al. 2022

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The kinetics of hydride transfer from Re( R bpy)-(CO) 3 H (bpy = 4,4′-R-2,2′-bipyridine; R = OMe, t Bu, Me, H, Br, COOMe, CF 3 ) to CO 2 and seven different cationic N-heterocycles were determined. Additionally, the thermodynamic hydricities of complexes of the type Re( R bpy)(CO) 3 H were established primarily using computational methods. Linear free-energy relationships (LFERs) derived by correlating thermodynamic and kinetic hydricities indicate that, in general, the rate of hydride transfer increases as the thermodynamic driving force for the reaction increases. Kinetic isotope effects range from inverse for hydride transfer reactions with a small driving force to normal for reactions with a large driving force. Hammett analysis indicates that hydride transfer reactions with greater thermodynamic driving force are less sensitive to changes in the electronic properties of the metal hydride, presumably because there is less buildup of charge in the increasingly early transition state. Bronsted α values were obtained for a range of hydride transfer reactions and along with DFT calculations suggest the reactions are concerted, which enables the use of Marcus theory to analyze hydride transfer reactions involving transition metal hydrides. It is notable, however, that even slight perturbations in the steric properties of the Re hydride or the hydride acceptor result in large deviations in the predicted rate of hydride transfer based on thermodynamic driving forces. This indicates that thermodynamic considerations alone cannot be used to predict the rate of hydride transfer, which has implications for catalyst design.

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Section: Introductionmentioning

confidence: 99%

Correlating Thermodynamic and Kinetic Hydricities of Rhenium Hydrides

et al. 2022

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“…The requirement of high pressurized equipment impedes the utilization of molecular H 2 on a bulk scale. 153 Hence, hydrogenation in the presence of a reagent that can act as a carrier of H 2 is intrinsically safe and can circumvent the use of specialized equipment. Mn-based catalytic systems in the area of transfer hydrogenation (TH) of ketones were first introduced by Beller in 2017 (Table 8, entry 1).…”

Section: Manganese-catalyzed Hydrogenation Reactionsmentioning

confidence: 99%

Manganese-catalyzed hydrogenation, dehydrogenation, and hydroelementation reactions

et al. 2022

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“…[1] Catalytic TH, where a proton and hydride are transferred from substrate to acceptor, is an important transformation with applications that include the synthesis of fine chemicals and of pharmaceuticals. [2] Most often those reactions are carried out by molecular Ru, Rh, and Ir complexes, and recent work has used earth-abundant elements, such as Mn, Fe, Ni, and Co. [3] After more than two decades since the Nobel-Prize-winning developments in asymmetric TH (ATH) by Noyori, [4] molecular catalysts centered on Ru have remained of great interest to the chemical community. The origin of enantioselectivity is a result of a dynamic interplay of noncovalent interactions within the transition state that ultimately determines enantiomeric excess.…”

Section: Introductionmentioning

confidence: 99%

Aluminum‐Ligand Cooperative O−H Bond Activation Initiates Catalytic Transfer Hydrogenation

et al. 2022

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Molecular design ultimately furnishes improvements in performance over time, and this has been the case for Rh-and Irbased molecular catalysts currently used in transfer hydrogenation (TH) reactions for fine chemical synthesis. In this report, we describe a molecular pincer ligand Al catalyst for TH, (I 2 P 2À )Al(THF)Cl (I 2 P = diiminopyridine; THF = tetrahydrofuran). The mechanism for TH is initiated by two successive Al-ligand cooperative bond activations of the OÀ H bonds in two molecules of isopropanol ( i PrOH) to afford six-coordinate (H 2 I 2 P)Al(O i Pr) 2 Cl. Stoichiometric chemical reactions and kinetic experiments suggest an ordered transition state, supported by polar solvents, for concerted hydride transfer from i PrO À to substrate. Metal-ligand cooperative hydrogen bonding in a cyclic transition state is a likely support for the concerted hydride transfer event. The available data does not support involvement of an intermediate Al-hydride in the TH. Proof-ofprinciple reactions including the conversion of isopropanol and benzophenone to acetone and diphenylmethanol with 90 % conversion in 1 h are described. The analogous hydride compound, (I 2 P 2À )Al(THF)H, also cleaves the OÀ H bond in i PrOH to afford (HI 2 P À )Al(O i Pr)H and (HI 2 P À )Al(O i Pr) 2 , but no activity for catalytic TH was observed.

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Recent advances in homogeneous base-metal-catalyzed transfer hydrogenation reactions

Cited by 41 publications

References 156 publications

Correlating Thermodynamic and Kinetic Hydricities of Rhenium Hydrides

Correlating Thermodynamic and Kinetic Hydricities of Rhenium Hydrides

Manganese-catalyzed hydrogenation, dehydrogenation, and hydroelementation reactions

Aluminum‐Ligand Cooperative O−H Bond Activation Initiates Catalytic Transfer Hydrogenation

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