19214-96-1Relevant articles and documents
Imbalanced tunneling ready states in alcohol dehydrogenase model reactions: Rehybridization lags behind H-tunneling
Hammann, Blake,Razzaghi, Mortezaali,Kashefolgheta, Sadra,Lu, Yun
, p. 11337 - 11339 (2012)
The secondary kinetic isotope effects for the hydride transfer reactions from aliphatic alcohols to two carbocations (NAD+ models) in acetonitrile were determined. The results suggest that the hydride transfer takes place by tunneling and that the rehybridizations of both donor and acceptor carbons lag behind the H-tunneling. This is quite contrary to the observations in alcohol dehydrogenases where the importance of enzyme motions in catalysis is manifested.
A new mechanism of metal-ligand cooperative catalysis in transfer hydrogenation of ketones
Cherepakhin, Valeriy,Demianets, Ivan,Lauridsen, Paul J.,Maertens, Alexander,Mallikarjun Sharada, Shaama,Williams, Travis J.
, (2020)
We report iridium catalysts IrCl(η5-Cp?)(κ2-(2-pyridyl)CH2NSO2C6H4X) (1-Me, X = CH3 and 1-F, X = F) for transfer hydrogenation of ketones with 2-propanol that operate by a previously unseen metal-ligand cooperative mechanism. Under the reaction conditions, complexes 1 (1-Me and 1-F) derivatize to a series of catalytic intermediates: Ir(η5-Cp?)(κ2-(C5H4N)CHNSO2Ar) (2), IrH(η5-Cp?)(κ2-(2-pyridyl)CH2NSO2Ar) (3), and Ir(η5-Cp?)(κ3-(2-pyridyl)CH2NSO2Ar) (4). The structures of 1-Me and 4-Me were established by single-crystal X-ray diffraction. A rate-determining, concerted hydrogen transfer step (2 + R2CHOH ? 3 + R2CO) is suggested by kinetic isotope effects, Eyring parameters (ΔH≠ = 29.1(8) kcal mol?1 and ΔS≠ = ?17(19) eu), proton-hydride fidelity, and DFT calculations. According to DFT, a nine-membered cyclic transition state is stabilized by an alcohol molecule that serves as a proton shuttle.
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Condon
, p. 4675 (1951)
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Inherent asymmetry of constitutionally equivalent methyl groups in the H/D equilibration of n- and i-C3H7Fe(OH)+ complexes
Trage, Claudia,Zummack, Waltraud,Schroeder, Detlef,Schwarz, Helmut
, p. 2708 - 2710 (2007/10/03)
Transiently formed, constitutionally identical methyl groups remain inequivalent in the course of an n-propyl?isopropyl isomerization (see scheme) operative in Fe÷-mediated dehydration of propanols. The reversibility of the β-hydrogen transfer steps is addressed by examination of the H/D equilibration in metastable complexes of Fe+ with a set of selectivity deuterated propanols by using tandem mass spectrometry.