Efficient Transfer Hydrogenation Research Articles

Highly Diastereoselective Formation of Ruthenium Complexes for Efficient Catalytic Asymmetric Transfer Hydrogenation

Jumping Josiphos! Ruthenium cis-dichloro complexes with matched chiral diphosphane and aminopyridine ligands (see structure) are easily obtained by a one-pot reaction of [RuCl2(PPh3)3] with a Josiphos diphosphane and racemic 1-substituted 1-(pyridin-2-yl)methanamine ligands. These complexes are highly active catalysts for the transfer hydrogenation of ketones, affording turnover frequencies of up to 70 000 h−1 at 60 °C and ee values up to 99 %. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2007/z702278_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Mixture of poly(ethylene glycol) and water as environmentally friendly media for efficient enantioselective transfer hydrogenation and catalyst recycling

The asymmetric transfer hydrogenation of nonfunctionalized aromatic ketones catalyzed by Ru-TsDPEN was performed successfully in a mixture of poly(ethylene glycol) (PEG) and water. High activity and enantioselectivity were obtained, which were better than or comparable to those obtained in conventional organic solvents. The unmodified catalyst could be easily recovered after extraction of the reduced product with a less polar solvent such as hexane, and was reused at least 14 times without obvious loss in enantioselectivity. These results indicate that the inexpensive and non-toxic aqueous PEG can serve as a new means for the immobilization of Ru-TsDPEN catalyst and related variants without calling for catalyst modification.

Efficient Transfer Hydrogenation of Ketones in the Presence of Ruthenium N‐Heterocyclic Carbene Catalysts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Physical, Crystallographic, and Spectroscopic Characterization of a Crystalline Pharmaceutical Hydrate: Understanding the Role of Water

The single-crystal X-ray diffraction structure of the sodium salt of N-(3-(aminosulfonyl)-4-chloro-2-hydroxyphenyl)-N‘-(2,3-dichlorophenyl) urea at 173 K is reported. The structure contains 3 mol of water situated in distinct channels in the vicinity of the sodium cation. Powders of this phase undergo isomorphic dehydration, losing 0.5% w/w water between 90 and 15% relative humidity (RH) at 25 °C without changing the powder X-ray pattern. Below 15% RH and above 50 °C, additional dehydration occurs in conjunction with a reversible phase transition. A third semicrystalline dehydrated phase appears after vacuum-drying and at high temperatures and also can be reversibly rehydrated to the original form. Single crystals of the dehydrated phases could not be prepared, so a combination of methods were used to understand the structural changes occurring during the desolvation process, including thermal analysis, vapor sorption measurements, variable-humidity and variable-temperature powder X-ray diffraction, vibrational spectroscopy, and 1H, 13C, 15N, and 23Na magic-angle spinning (MAS) solid-state NMR. The uptake of water vapor into the trihydrate form was investigated by NMR and vibrational spectroscopy using isotopically labeled water. Static 2H and 17O NMR quadrupolar line shape analysis combined with changes in MAS spectra showed exchanged sites on the parent and water molecules. The results indicate that two moles of ion-associated water in the larger tunnel are more labile than a hydrogen-bonded mole of water. Entire water molecules can exchange into the lattice to a small extent, but more efficient hydrogen transfer exchange is observed in the main channel and a smaller perpendicular side channel. The exchanged water deuterons execute rapid three-site jump motions at 273 K.

Efficient transfer hydrogenation of ketones in the presence of ruthenium N-heterocyclic carbene catalysts

Novel ruthenium carbene complexes have been in situ generated and tested for the transfer hydrogenation of ketones. Applying Ru(cod)(methylallyl) 2 in the presence of imidazolium salts in 2-propanol and sodium-2-propanolate as base, turnover frequencies up to 346 h −1 have been obtained for reduction of acetophenone. A comparative study involving ruthenium carbene and ruthenium phosphine complexes demonstrated the higher activity of ruthenium carbene complexes.

Efficient Heterogeneous Asymmetric Transfer Hydrogenation Catalyzed by Recyclable Silica‐Supported Ruthenium Complexes.

Easily accessible N-(p-tolylsulfonyl)-1,2-diphenylethylenediamine-(TsDPEN-)derived organic–inorganic hybrid ligands were prepared and applied to the heterogeneous asymmetric transfer hydrogenation in traditional HCO2H/NEt3 and in water with HCO2Na as the hydrogen source and sodium dodecyl sulfate (SDS) as the phase-transfer catalyst. The reactions demonstrated high catalytic activities and excellent enantioselectivities for most aromatic ketones and the imine tested, with results similar to those in homogeneous catalysis.In particular, this heterogeneous catalyst can be readily recovered and used in multiple consecutive catalytic runs with the high enantioselectivity maintained both in HCO2H/NEt3 and in water. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Highly Efficient Asymmetric Transfer Hydrogenation of Ketones Catalyzed by Chiral “Roofed” cis‐Diamine—Ru(II) Complex.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Polymer‐Supported Formate and Magnesium: An Efficient Transfer Hydrogenation System for the Facile Reduction of Azo Compounds.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Efficient Heterogeneous Asymmetric Transfer Hydrogenation Catalyzed by Recyclable Silica‐Supported Ruthenium Complexes

AbstractEasily accessible N‐(p‐tolylsulfonyl)‐1,2‐diphenylethylenediamine‐(TsDPEN‐)derived organic–inorganic hybrid ligands were prepared and applied to the heterogeneous asymmetric transfer hydrogenation in traditional HCO2H/NEt3 and in water with HCO2Na as the hydrogen source and sodium dodecyl sulfate (SDS) as the phase‐transfer catalyst. The reactions demonstrated high catalytic activities and excellent enantioselectivities for most aromatic ketones and the imine tested, with results similar to those in homogeneous catalysis.In particular, this heterogeneous catalyst can be readily recovered and used in multiple consecutive catalytic runs with the high enantioselectivity maintained both in HCO2H/NEt3 and in water. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Highly efficient asymmetric transfer hydrogenation of ketones catalyzed by chiral ‘roofed’ cis-diamine–Ru(II) complex

A new type of chiral Ru(II) complex, prepared from a conformationally rigid, sterically bulky ‘roofed’ cis-diamine and [RuCl 2(benzene)] 2, functions as an efficient catalyst for the asymmetric transfer hydrogenation of a wide variety of aryl ketones, including sterically bulky ketones, when the reaction is conducted in the presence of 5HCO 2H·2NEt 3.

Highly Efficient and Recyclable Heterogeneous Asymmetric Transfer Hydrogenation of Ketones in Water.

A highly efficient heterogeneous asymmetric transfer hydrogenation of ketones in water was developed for the first time, which exhibited excellent enantioselectivities, distinct acceleration effect and remarkably high recyclabilities.

Polymer-Supported Formate and Magnesium: An Efficient Transfer Hydrogenation System for the Facile Reduction of Azo Compounds

A mild and efficient method was developed for the chemo-selective reduction of azo compounds to the corresponding amine/s using recyclable polymer-supported formate as hydrogen donor in the presence of low cost magnesium powder at room temperature.

Efficient Transfer Hydrogenation of Ketones Catalyzed by the Bis(isocyanide)−Ruthenium(II) Complexes trans,cis,cis-[RuX2(CNR)2(dppf)] (X = Cl, Br; dppf = 1,1‘-Bis(diphenylphosphino)ferrocene): Isolation of Active Mono- and Dihydride Intermediates

The bis(isocyanide)−ruthenium(II) complexes trans,cis,cis-[RuX2(CNR)2(dppf)] (X = Cl, R = CH2Ph (2a), Cy (2b), tBu (2c), 2,6-C6H3Me2 (2d), (S)-(−)-C(H)MePh (2e); X = Br, R = CH2Ph (3a), Cy (3b), tBu (3c), 2,6-C6H3Me2 (3d), (S)-(−)-C(H)MePh (3e)) have been prepared by reaction of the bis(allyl)−ruthenium(II) derivative [Ru(η3-2-C3H4Me)2(dppf)] (1) with the appropriate isocyanide ligand, in CH2Cl2 at room temperature and in the presence of the corresponding hydrogen halide HX. The structure of the compound trans,cis,cis-[RuCl2(CN-2,6-C6H3Me2)2(dppf)] (2d) has been confirmed by X-ray crystallography. The catalytic activity of complexes 2a−e and 3a−e in the transfer hydrogenation of acetophenone by propan-2-ol has been studied, and the most active complex, trans,cis,cis-[RuCl2(CNCH2Ph)2(dppf)] (2a), has been also tested as a catalyst in the transfer hydrogenation of a large variety of ketones. The hydride derivatives cis,cis-[RuHCl(CN-2,6-C6H3Me2)2(dppf)] (4) and cis,cis,cis-[RuH2(CN-2,6-C6H3Me2)2(dppf)] (5) have been isolated and characterized. Although both hydride complexes catalyze the transfer hydrogenation of acetophenone in the absence of base, the reactions proceed ca. 5 times faster with 5 than with 4, pointing out that the real active species are dihydride−ruthenium complexes.

Efficient Asymmetric Transfer Hydrogenation of Activated Olefins Catalyzed by Ruthenium Amido Complexes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Efficient Heterogeneous Asymmetric Transfer Hydrogenation of Ketones Using Highly Recyclable and Accessible Silica‐Immobilized Ru‐TsDPEN Catalysts.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Borrowing Hydrogen: A Catalytic Route to C—C Bond Formation from Alcohols.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Efficient asymmetric transfer hydrogenation of activated olefins catalyzed by ruthenium amido complexes

The asymmetric transfer hydrogenation of activated olefins with chiral ruthenium amido complexes (Noyori catalyst) using formic acid–triethylamine azeotrope as hydrogen source resulted in excellent yields and high enantioselectivities (up to 88.5%).

Highly efficient and recyclable heterogeneous asymmetric transfer hydrogenation of ketones in water.

A highly efficient heterogeneous asymmetric transfer hydrogenation of ketones in water was developed for the first time, which exhibited excellent enantioselectivities, distinct acceleration effect and remarkably high recyclabilities.

Borrowing hydrogen: a catalytic route to C-C bond formation from alcohols.

Ruthenium complexes have been shown to perform efficient transfer hydrogenation reactions between alcohols and alkenes; in combination with an in situ Wittig reaction, indirect formation of C-C bonds has been achieved from alcohols.

Efficient heterogeneous asymmetric transfer hydrogenation of ketones using highly recyclable and accessible silica-immobilized Ru-TsDPEN catalysts.

[reaction: see text] Chiral Ru-TsDPEN [N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine]-derived catalysts were first successfully immobilized onto amorphous silica gel and mesoporous silicas of MCM-41 and SBA-15 by an easily accessible approach. The catalyst immobilized on silica gel demonstrated remarkably high catalytic activities and excellent enantioselectivities (up to >99% ee) for the heterogeneous asymmetric transfer hydrogenation of various ketones. Particularly, the catalyst could be readily recovered and reused in multiple consecutive catalytic runs (up to 10 uses) with the completely maintained enantioselectivity.