Structural characterisation of a transient intermediate in rhodium-catalysed asymmetric homogeneous hydrogenation

Brown, John M.; Chaloner, Penny A.

doi:10.1039/c39800000344

Cited by 127 publications

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“…Consequently, the stereochemistry of the hydrogenation is regulated by this relative reactivity rather than by the relative thermodynamic stability of the diastereomers [73,75,77]. Halpern and Landis accomplished detailed kinetic measurements on the hydrogenation of methyl-(Z)-a-acetamidocinnamate [(Z)-MAC] enamide catalyzed by Rh(DIPAMP) species.…”

Section: Hydrogenation Of Iminesmentioning

confidence: 99%

Rhodium

and¹,

Carmona²

2006

The Handbook of Homogeneous Hydrogenation

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Monohydride (MH) catalysts, such as [RhH(CO)(PPh 3 ) 3 ], react with substrates such as alkenes, according to Scheme 1.1, yielding rhodium-alkyl intermediates which, by subsequent reaction with hydrogen, regenerate the initial monohydride catalyst. This mechanism is usually adopted by hydrogenation catalysts which contain an M-H bond. Dihydride Hydrogenation CatalystsMany of these catalysts are derived from metal complexes which, initially, do not contain metal hydride bonds, but can give rise to intermediate MH 2 (alkene) species. These species, after migratory insertion of the hydride to the coordinated alkene and subsequent hydrogenolysis of the metal alkyl species, yield the saturated alkane. At first glance there are two possibilities to reach MH 2 (alkene) intermediates which are related to the order of entry of the two reaction partners in the coordination sphere of the metal (Scheme 1.2).

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Section: Hydrogenation Of Iminesmentioning

confidence: 99%

Rhodium

and¹,

Carmona²

2006

The Handbook of Homogeneous Hydrogenation

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“…[76][77][78] A decrease in the reaction rate due to a stronger binding interaction between the sulfonate groups from the resin and the rhodium centres, after NBD has been reduced and replaced by weaker ligands in the first hydrogenation step, was hypothesised on these basis. However, the absence of any other resonance prevented an unambiguous explanation for the decreased catalytic activity.…”

Section: H T U N G T R E N N U N G (Tmbtp)a C H T U N G T R E N N U Nmentioning

confidence: 98%

Recycling Asymmetric Hydrogenation Catalysts by Their Immobilization onto Ion‐Exchange Resins

Barbaro

2006

Chemistry A European J

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“…Among them, the cationic Rh-diphosphane-enamide complex [7,10,14] and the alkyl monohydride species [8,12] have been characterised by various spectroscopic and X-ray-based methods. Also, the presumed dihydride intermediate has been investigated by PHIP (para-hydrogen induced polarisation) NMR spectroscopy, which is a powerful tool for studying hydrogenation reactions.…”

Section: Introductionmentioning

confidence: 99%

“…Chemical, [7][8][9][10][11][12][13][14] kinetic [9] and theoretical [15,16] studies have been carried out. As a result, the rhodium-catalysed hydrogenation of dehydroamino acids leading to enantiomerically pure α-amino acids is considered to be a thoroughly understood reaction based on work carried out in- the research groups of Halpern [7] and Brown [8] who revealed the underlying steps of the process. It has been demonstrated that the minor diastereomer resulting from the coordination of the enamide to the cationic Rh-diphosphane precursor reacts more rapidly with molecular hydrogen providing the observed prevailing hydrogenated product.…”

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confidence: 99%

A Density Functional Study of the Hydrogenation of Ketones Catalysed by Neutral Rhodium‐Diphosphane Complexes

Agbossou‐Niedercorn

Paul

2006

Eur J Inorg Chem

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International audienceThe potential energy profile of RhI-catalysed hydrogenation of ketones has been computed for the simple model system [Rh{H3POCH2CH2N(H)PH3}(Cl)] using DFT calculations. The general sequence of the catalytic cycle involves coordination of the carbonyl derivative to the neutral RhI complex followed by oxidative addition of molecular hydrogen providing rhodium dihydride intermediates. The latter are converted into alkoxy hydrides by a migratory insertion reaction. Reductive elimination of the alcohol and substitution of the latter by the incoming substrate completes the catalytic cycle. Intermediates and transition states of all catalytic steps have been located. Two isomeric derivatives bearing the model substrate have been found for the [Rh{H3POCH2CH2N(H)PH3}(Cl)(H2CO)] complex. Eight diastereomeric pathways have been followed for the cis addition of molecular hydrogen to [Rh{H3POCH2CH2N(H)PH3}(Cl)- (H2CO)] leading to eight distinct isomeric dihydride intermediates. Four dihydride complexes can be considered as the more accessible compounds. The site preference for migratory insertion and transition states discriminates the main path of the catalytic reaction. Migratory insertion to form the alkoxy hydride constitute the turn over limiting step of the process. The potential energy profile has been found to be smooth without excessive activation barriers

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Structural characterisation of a transient intermediate in rhodium-catalysed asymmetric homogeneous hydrogenation

Cited by 127 publications

References 0 publications

Rhodium

Rhodium

Recycling Asymmetric Hydrogenation Catalysts by Their Immobilization onto Ion‐Exchange Resins

A Density Functional Study of the Hydrogenation of Ketones Catalysed by Neutral Rhodium‐Diphosphane Complexes

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