Mechanism of hydrogen transfer in the reduction of the imine bond by an NADH model. Use of cyclopropane ring as a chemical probe

Niel, J. C. G. van; Pandit, U. K.

doi:10.1039/c39830000149

Cited by 12 publications

(3 citation statements)

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“…Keywords: density functional calculations · hydrogenation · imines · organocatalysis · pyridines pendent enzymes. [4] Whether NAD(P)H reacts according to a radical or a hydride transfer mechanism has been at the center of scientific debate for many years. Today, there is still no universal consensus about this issue.…”

Section: Introductionmentioning

confidence: 99%

Phosphoric Acid Catalyzed Enantioselective Transfer Hydrogenation of Imines: A Density Functional Theory Study of Reaction Mechanism and the Origins of Enantioselectivity

Marcelli

Hammar

Himo

2008

Chemistry A European J

164

114

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The phosphoric acid catalyzed reaction of 1,4-dihydropyridines with N-arylimines has been investigated by using density functional theory. We first considered the reaction of acetophenone PMP-imine (PMP=p-methoxyphenyl) with the dimethyl Hantzsch ester catalyzed by diphenyl phosphate. Our study showed that, in agreement with what has previously been postulated for other reactions, diphenyl phosphate acts as a Lewis base/Brønsted acid bifunctional catalyst in this transformation, simultaneously activating both reaction partners. The calculations also showed that the hydride transfer transition states for the E and Z isomers of the iminium ion have comparable energies. This observation turned out to be crucial to the understanding of the enantioselectivity of the process. Our results indicate that when using a chiral 3,3'-disubstituted biaryl phosphoric acid, hydride transfer to the Re face of the (Z)-iminium is energetically more favorable and is responsible for the enantioselectivity, whereas the corresponding transition states for nucleophilic attack on the two faces of the (E)-iminium are virtually degenerate. Moreover, model calculations predict the reversal in enantioselectivity observed in the hydrogenation of 2-arylquinolines, which during the catalytic cycle are converted into (E)-iminium ions that lack the flexibility of those derived from acyclic N-arylimines. In this respect, the conformational rigidity of the dihydroquinolinium cation imposes an unfavorable binding geometry on the transition state for hydride transfer on the Re face and is therefore responsible for the high enantioselectivity.

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Section: Introductionmentioning

confidence: 99%

Phosphoric Acid Catalyzed Enantioselective Transfer Hydrogenation of Imines: A Density Functional Theory Study of Reaction Mechanism and the Origins of Enantioselectivity

Marcelli

Hammar

Himo

2008

Chemistry A European J

164

114

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“…The Hantzsch ester ( 1 ) and analogues have been employed as NADH models but not as frequently as BNAH or AcrH 2 . − This is probably due to there being an additional mechanistic complexity regarding which of the two different hydrogen atoms (from the 1- or 4-positions) is first transferred in the reduction process. A number of isotope-labeling studies have pointed to initial dehydrogenation taking place at the 4-position. ,− ,, However, there is also compelling evidence supporting the initial loss of hydrogen from the 1-nitrogen in certain oxidations of derivatives of 1 . , …”

Section: Introductionmentioning

confidence: 99%

“…A number of isotope-labeling studies have pointed to initial dehydrogenation taking place at the 4-position. 30,[44][45][46]49,50 However, there is also compelling evidence supporting the initial loss of hydrogen from the 1-nitrogen in certain oxidations of derivatives of 1. 51,52 Recently, Zhu, Cheng, and co-workers described their findings with respect to the oxidation mechanism of 1 by ethyl R-cyanocinnamates and benzylidenemalononitriles where they concluded that the reduction of the R,βunsaturated substrates was initiated by hydride transfer from C-4 of 1.…”

Section: Introductionmentioning

confidence: 99%

Synthetic and Theoretical Studies on the Reduction of Electron Withdrawing Group Conjugated Olefins Using the Hantzsch 1,4-Dihydropyridine Ester

et al. 2003

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The Hantzsch 1,4-dihydropyridine ester (1) has been observed to be a useful selective reducing agent for the reduction of electron-withdrawing conjugated double bonds. The rate of this reaction was observed to be dependent upon the nature of the conjugated substituents and, consequently, the electronic nature of the unsaturated double bond. Theoretical calculations confirmed the importance of the HOMO-LUMO gap for this reaction and implicated a hydride transfer, agreeing with the experimentally observed reaction rate order. The calculations also revealed the importance of a boatlike structure of the 1,4-dihydropyridine nucleus as well as a trans arrangement of the ester groups to facilitate the hydride transfer.

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Temperature dependence of the primary kinetic isotope effect for hydride transfer mediated by a NAD(P)H‐model; discrimination between bent and linear transition states

Gerresheim

Verhoeven

1983

Recl. Trav. Chim. Pays‐Bas

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Mechanism of hydrogen transfer in the reduction of the imine bond by an NADH model. Use of cyclopropane ring as a chemical probe

Cited by 12 publications

References 0 publications

Phosphoric Acid Catalyzed Enantioselective Transfer Hydrogenation of Imines: A Density Functional Theory Study of Reaction Mechanism and the Origins of Enantioselectivity

Phosphoric Acid Catalyzed Enantioselective Transfer Hydrogenation of Imines: A Density Functional Theory Study of Reaction Mechanism and the Origins of Enantioselectivity

Synthetic and Theoretical Studies on the Reduction of Electron Withdrawing Group Conjugated Olefins Using the Hantzsch 1,4-Dihydropyridine Ester

Temperature dependence of the primary kinetic isotope effect for hydride transfer mediated by a NAD(P)H‐model; discrimination between bent and linear transition states

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