Heterogeneous catalytic transfer hydrogenation and its relation to other methods for reduction of organic compounds

Johnstone, R. A. W.; Wilby, Anna H.; Entwistle, Ian D.

doi:10.1021/cr00066a003

Cited by 948 publications

(427 citation statements)

References 91 publications

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] From a fundamental point of view, tetrazoles are also particularly interesting systems, especially because of the tautomerism they may exhibit and their diversified photochemistry. 1,[21][22][23][24][25][26][27][28][29] Unsubstituted tetrazole, for example, was found to exist exclusively in the crystalline phases as the 1H-tautomer, [30][31][32] whereas in solution and gas phase 1H-and 2H-tautomers coexist, the population of the most polar 1H form increasing with the polarity of the solvent.…”

Section: Introductionmentioning

confidence: 99%

Tautomer Selective Photochemistry in 1-(Tetrazol-5-yl)ethanol

et al. 2010

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A combined matrix isolation FTIR and theoretical DFT/B3LYP/6-311++G(d,p) study of the molecular structure and photochemistry of 1-(tetrazol-5-yl)ethanol [1-TE] was performed. The potential energy surface landscapes of the 1H and 2H tautomers of the compound were investigated and the theoretical results were used to help characterize the conformational mixture existing in equilibrium in the gas phase prior to deposition of the matrices, as well as the conformers trapped in the latter. In the gas phase, at room temperature, the compound exists as a mixture of 12 conformers (five of the 1H tautomer and seven of the 2H tautomer). Upon deposition of the compound in an argon matrix at 10 K, only three main forms survive, because the low barriers for conformational isomerization allow extensive conformational cooling during deposition. Deposition of the matrix at 30 K led to further simplification of the conformational mixture with only one conformer of each tautomer of 1-TE surviving. These conformers correspond to the most stable forms of each tautomer, which bear different types of intramolecular H-bonds: 1H-I has an NH · · · O hydrogen bond, whereas 2H-I has an OH · · · N hydrogen bond. Upon irradiating with UV light (λ > 200 nm), a matrix containing both 1H-I and 2H-I forms, an unprecedented tautomer selective photochemistry was observed, with the 2H tautomeric form undergoing unimolecular decomposition to azide + hydroxypropanenitrile and the 1H-tautomer being photostable.

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Section: Introductionmentioning

confidence: 99%

Tautomer Selective Photochemistry in 1-(Tetrazol-5-yl)ethanol

et al. 2010

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“…Catalytic transfer hydrogenation (CTH) has been found to be an efficient and selective method to synthesize unsaturated alcohols [8][9][10]. Metal oxides, MgO [11,12], ZrO 2 [13], double layered hydroxides [14], MgO-B 2 O 3 [15], and Al 2 O 3 -AlPO 4 [16] have been used as catalysts.…”

Section: Introductionmentioning

confidence: 99%

Reactivity of Alcohols in Chemoselective Transfer Hydrogenation of Acrolein over Magnesium Oxide as the Catalyst

Gliński

Ulkowska

2010

Catal Lett

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This paper presents the first full thermodynamic description of the hydrogen transfer between acrolein, the simplest a,b-unsaturated aldehyde, and a set of aliphatic alcohols, both primary and secondary. The vapour phase transfer hydrogenation of acrolein into allyl alcohol with various primary and secondary aliphatic alcohols used as hydrogen donors in the presence of MgO as the catalyst has been studied. Despite differentiated reactivity exhibited by these alcohols, a high chemoselectivity ([80%) to allyl alcohol has been observed for all of them. On the basis of thermodynamic calculations it has been found that secondary alcohols as hydrogen donors are more reactive than primary ones. However, ethanol or butan-1-ol have shown the highest reactivity. In their presence yields of allyl alcohol higher than 60% have been noted, which greatly exceed those predicted by thermodynamic calculations based on the following equation: acrolein ? ethanol (butan-1-ol) ? allyl alcohol ? acetaldehyde (butyraldehyde). Although similar yields have been reported in literature, no subsequent nor side reactions have been discussed even though the attained yield cannot be accounted for by this reaction alone. As a possible explanation of the discrepancy the occurrence of a disregarded reaction, for which DG \ 0, has been considered. It has been shown that aldol condensation fulfills these thermodynamic requirements, however, the products of this reaction are noted only at the beginning of the process and the decrease of their amount does not influence the yield of allyl alcohol.

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“…Less well known and utilized is Raney nickel's ability to catalyze reductions using hydrogen donors instead of molecular hydrogen [3,4]. Known as catalytic transfer hydrogenation, this remarkable reaction was first described 50 years ago by Kleiderer and Kornfeld [5] in their study on the Raney nickel catalyzed transfer of hydrogen from cholesterol to cyclohexanone.…”

Section: Introductionmentioning

confidence: 99%

Transfer hydrogenolysis of aromatic alcohols using Raney catalysts and 2-propanol

Gross

Mebane

Armstrong

2001

Applied Catalysis A: General

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Raney nickel in refluxing 2-propanol is an effective catalytic system for cleaving C-O bonds in aromatic alcohols by transfer hydrogenolysis. Deoxygenation of alcohols substituted at the ␣-, ␤-, ␥-, ␦-, and ε-positions was accomplished. The reaction appears not to be sensitive to substitution about the carbinol carbon. Aliphatic alcohols do not undergo hydrogenolysis with this system. Some dehydromethylation is found in the hydrogenolysis of primary alcohols. With extended reaction times, ring reduction accompanies hydrogenolysis of alcohols containing more than one aromatic ring. Raney cobalt is shown to catalyze hydrogen transfer from 2-propanol. Raney cobalt in refluxing 2-propanol is an effective system for deoxygenating ␣-substituted alcohols only. Although Raney cobalt is less reactive than Raney nickel in transfer hydrogenolysis, it exhibits greater selectivity as illustrated by the lack of ring reduction in alcohols containing more than one aromatic ring.

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Heterogeneous catalytic transfer hydrogenation and its relation to other methods for reduction of organic compounds

Cited by 948 publications

References 91 publications

Tautomer Selective Photochemistry in 1-(Tetrazol-5-yl)ethanol

Tautomer Selective Photochemistry in 1-(Tetrazol-5-yl)ethanol

Reactivity of Alcohols in Chemoselective Transfer Hydrogenation of Acrolein over Magnesium Oxide as the Catalyst

Transfer hydrogenolysis of aromatic alcohols using Raney catalysts and 2-propanol

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