Diastereoselective hydrogenation of substituted aromatics on supported rhodium catalysts: influence of support and of thermal treatment

Бессон, М.; Gallezot, P.; Pinel, Catherine; Neto, Samuel

doi:10.1016/s0167-2991(97)80907-x

Cited by 14 publications

(5 citation statements)

References 7 publications

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“…From XPS it was also determined that rhodium is only present in the oxidation state (I); no traces of metallic rhodium(0) were found in the samples . The binding energies of the rhodium 3d electrons in 1 (I) + were found to be 312 and 317 eV with a relative intensity of 3.3 and 2.…”

Section: Resultsmentioning

confidence: 96%

A Silica-Supported, Switchable, and Recyclable Hydroformylation−Hydrogenation Catalyst

et al. 2001

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A homogeneous hydroformylation catalyst, designed to produce selectively linear aldehydes, was covalently tethered to a polysilicate support. The immobilized transition-metal complex [Rh(A)CO]+(1+)), in which A is N-(3-trimethoxysilane-n-propyl)-4,5-bis(diphenylphosphino)phenoxazine, was prepared both via the sol-gel process and by covalent anchoring to silica. 1+ was characterized by means of (31)P and (29)Si MAS NMR, FT-IR, and X-ray photoelectron spectroscopy. Polysilicate immobilized Rh(A) performed as a selective hydroformylation catalyst showing an overall selectivity for the linear aldehyde of 94.6% (linear to branched aldehyde ratio of 65). In addition 1-nonanol, obtained via the hydrogenation of the corresponding aldehyde, was formed as an unexpected secondary product (3.6% at 20% conversion). Under standard hydroformylation conditions, 1+ and HRh(A)(CO)(2)(1) coexist on the support. This dual catalyst system performed as a hydroformylation/hydrogenation sequence catalyst (Z), giving selectively 1-nonanol from 1-octene; ultimately, 98% of 1-octene was converted to mainly 1-nonanal and 97% of the nonanal was hydrogenated to 1-nonanol. The addition of 1-propanol completely changes Z in a hydroformylation catalyst (X), which produces 1-nonanal with an overall selectivity of 93%, and completely suppresses the reduction reaction. If the atmosphere is changed from CO/H(2) to H(2) the catalyst system is switched to the hydrogenation mode (Y), which shows a clean and complete hydrogenation of 1-octene and 1-nonanal within 24 h. The immobilized catalyst can be recycled and the system can be switched reversibly between the three "catalyst modes" X, Y, and Z, completely retaining the catalyst performance in each mode.

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Section: Resultsmentioning

confidence: 96%

A Silica-Supported, Switchable, and Recyclable Hydroformylation−Hydrogenation Catalyst

et al. 2001

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“…The mode of adsorption of the aromatic substrate onto the unshielded face of the aromatic ring dictates the major configuration of the hydrogenation product. However, as already noted with the prolinate auxiliary, [22] an additional anchoring interaction between the oxygen atoms (ester group and benzoic carbonyl) and the ruthenium metallic surface, which is more electropositive than rhodium, may still promote a preferential adsorption of the molecule onto one specific face. This leads to an enhancement of the diastereoselectivity.…”

mentioning

confidence: 66%

“…TEM and XPS studies have shown that in Rh/Al 2 O 3 , the rhodium particles have a flat morphology and that there are partially oxidised species present. [22] As proposed in the case of prolinate auxiliary, [22] this promoting effect may be attributed to a stronger interaction between the rhodium atoms with a low valence state on alumina and the oxygenated groups of the ester, which optimises the adsorptive effect.…”

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confidence: 94%

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Asymmetric Synthesis of 2-Methyl Cyclohexane Carboxylic Acids by Heterogeneous Catalysis: Mechanistic Aspects

et al. 2000

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The catalytic hydrogenation of (S)-alkyl-N-(2-methylbenzoyl)pyroglutamates was studied over supported rhodium and ruthenium catalysts at room temperature and a pressure of 5 MPa. The reaction was diastereoselective with the predominant formation of (1S,2R)-2-methylcyclohexane carboxylic acid with a diastereomeric excess (de) of up to 96%. The most stable conformation was determined by means of a combination of modelling calculations, NMR spectroscopy and X-ray structural determination. In this conformation, the carbonyl group of the pyroglutamate auxiliary shields one face of the aromatic ring. The observed selectivity may thus be explained by a preferential adsorption at the unshielded face which avoids steric repulsion by the C=O group to result in a cis hydrogenation. The addition of an amine, the nature of the support (alumina or active carbon) or of the metal (Rh or Ru) were shown to give additional stabilisation of the adsorption at the unshielded face to increase the diastereoisomeric excess.

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“…Besson et al made a thorough study of the diastereoselective hydrogenation of o-toluic acid coupled to many different types of proline auxiliaries [85][86][87][88]. Hydrogenation reactions were conducted at room temperature in alcoholic solvents and at 50 bar hydrogen pressure over either carbon-or aluminasupported rhodium catalysts.…”

Section: Diastereoselective Hydrogenation Of Substituted Aromaticsmentioning

confidence: 99%

Diastereoselective Hydrogenation in the Preparation of Fine Chemicals

Kukula¹,

Prins

2004

ChemInform

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Diastereoselective hydrogenation of substituted aromatics on supported rhodium catalysts: influence of support and of thermal treatment

Cited by 14 publications

References 7 publications

A Silica-Supported, Switchable, and Recyclable Hydroformylation−Hydrogenation Catalyst

A Silica-Supported, Switchable, and Recyclable Hydroformylation−Hydrogenation Catalyst

Asymmetric Synthesis of 2-Methyl Cyclohexane Carboxylic Acids by Heterogeneous Catalysis: Mechanistic Aspects

Diastereoselective Hydrogenation in the Preparation of Fine Chemicals

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