Dichlorotris(triphenylphosphine)ruthenium(II) catalyzed dehydrogenation of some natural products using cyclohexanone as acceptor
TL;DR: Cyclohexanone has been used as an acceptor for the dehydrogenation of some natural products in the presence of RuCl2(PPh3)3 as mentioned in this paper.
Abstract: Cyclohexanone has been used as an acceptor for the dehydrogenation of some natural products in the presence of RuCl2(PPh3)3. Only menthol undergoes appreciable dehydrogenation when compared to cholesterol and β-citronellol. Menthone, cholest-4-en-3-one and cholest-1,4-diene-3-one and citronellal are the products from these compounds. When carbohydrates are used as donors, in most cases the corresponding lactones are formed. The ratio of acceptor to donor is maintained at 6 in the latter cases to avoid disproportionation of the carbohydrates. Acids, isomer and epimer are formed in certain cases. It is observed that the dehydrogenation of carbohydrates is increased at elevated temperatures. The susceptibility to dehydrogenation of the carbohydrates is in the order sorbitol > mannitol > L-arabinose ≈ D-xylose > D-glucose ≈ sucrose > D-mannose ≈ D-galactose.
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TL;DR: In this paper, a mechanism for the transfer hydrogenation of ketones to secondary alcohols catalysed by HFe3(CO)11−1 (1) in the presence of Phase Transfer Catalysts (PTC) has been proposed using labelled hydrogen, NMR and IR techniques.
Abstract: A mechanism for the transfer hydrogenation of ketones to secondary alcohols catalysed by HFe3(CO)11−1 (1) in the presence of Phase Transfer Catalysts (PTC) has been proposed using labelled hydrogen, NMR and IR techniques.
36 citations
TL;DR: In the presence of trialkylamine and formic acid RuCl 2 (PPh 3 ) 3 selectively reduces aldehydes to the corresponding alcohols at room temperature as mentioned in this paper.
Abstract: In the presence of trialkylamine and formic acid RuCl 2 (PPh 3 ) 3 selectively reduces aldehydes to the corresponding alcohols at room temperature. Other reducible groups are unaffected.
27 citations
TL;DR: In this paper, a Ru-Zn catalyst for benzene selective hydrogenation to cyclohexene was presented, and the results showed that the catalyst was composed of Ru and Zn in molar ratio of 33.8:1 and the most probable value of the Ru crystallite size in the catalyst is 5.1 nm.
Abstract: A novel Ru-Zn catalyst was prepared by coprecipitation. The catalyst was characterized by XRF, XRD and TEM. The effects of organic additives on the performance of the Ru-Zn catalyst for benzene selective hydrogenation to cyclohexene were investigated. The results showed that the catalyst was composed of Ru and Zn in molar ratio of 33.8:1, and the most probable value of the Ru crystallite size in the catalyst was 5.1 nm. The modification of Ru with Zn and the small size effect were the main cause why the catalyst exhibited the high activity and the excellent cyclohexene selectivity. When PEG (polyethylene glycol) was used as an additive, the activity of the catalyst decreased, and the cyclohexene selectivity increased with the increase of the PEG molecular weight. With the addition of PEG-20000, a cyclohexene selectivity of 78.9% at a benzene conversion of 68.7% and a maximum cyclohexene yield of 61.4% were obtained. With diethanolamine and triethanolamine as additives, cyclohexene yields were as high as 58.9% and 58.2%, respectively.
23 citations
TL;DR: In this article, literature data and the investigation results of the present authors on the reduction of heterocyclic aldehydes and ketones using catalytic hydrogen transfer have been analyzed.
Abstract: Literature data and the investigation results of the present authors on the reduction of heterocyclic aldehydes and ketones using catalytic hydrogen transfer have been analyzed.
14 citations
TL;DR: In this paper, water-soluble homogeneous catalysts used for hydrogenation of aldehydes and aldoses are reviewed. Butler et al. focus on the mechanistic aspects of their activity and modes of their deactivation.
Abstract: Homogeneous catalysts used in hydrogenation of aldehydes and aldoses, mechanistic aspects of their activity, and modes of their deactivation are reviewed. Particular attention is paid to water soluble homogenous catalysts used for hydrogenation of sugars.
12 citations
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TL;DR: In this article, the dependence of the rate and the stereoselectivity on the complex, the concentrations of the water and KOH is studied in detail, and a reaction mechanism is proposed.
Abstract: Complexes of the type Ir(I)chelCODCl (chel = bipy; 4,4′-Me 2 bipy; phen; 4,7-Me 2 phen; 3,4,7,8-Me 4 phen; 4,7-Ph 2 Phen; COD = 1,5-cyclooctadiene) catalyze the hydrogen transfer from alcohols to ketones. The dependence of the rate and the stereoselectivity on the complex, the concentrations of the water and KOH is studied in detail, and a reaction mechanism is proposed. The most active of the above complexes is the 3,4,7,8-Me 4 phen derivative, which gaves turnovers of up to 1150 cycles/min and is still efficient at 4 X 10 −6 M concentration. Furthermore it favours the formation of the trans alcohol in the reduction of the t-butylcyclohexanone with high stereoselectivity.
56 citations
TL;DR: In this article, the asymmetric transfer reduction of prochiral ketones in homogeneous phase in the presence of H 4 Ru 4 (CO) 8 [(−)-DIOP] 2 as catalyst and secondary alcohols or indoline as hydrogen source is reported.
Abstract: The asymmetric transfer reduction of prochiral ketones in homogeneous phase in the presence of H 4 Ru 4 (CO) 8 [(−)-DIOP] 2 as catalyst and secondary alcohols or indoline as hydrogen source is reported. Optical yields up to 9.8% were obtained at 120° C. The reduction of ketones with molecular hydrogen under pressure affords alcohols at a higher rate but in lower optical yields.
45 citations