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A flexible, enantioselective route to highly functionalized α,β-unsaturated δ-lactones has been applied to the synthesis of 7-aza-phomopsolide E and its C-4 epimer. This approach relies on the application of the Noyori asymmetric hydrogenation of furyl ketone to produce the secondary furyl alcohol in high enantioexcess, which can be stereoselectively transformed into α,β-unsaturated-δ-lactones by a short, highly diastereoselective oxidation and reduction sequence. DCC and acid chloride couplings were used to introduce the side chains of the two natural product analogues.

The complexes [Ir(COD)(PR3)2]PF6 (R = PPh3 (1); R = PBn3 = tribenzylphosphine (2)), [Ir(COD)(PBn3)(PAn3)]PF6 (3) (PAn3 = Tri-orthoanisyl-phosphine) and cis-(P,P)-[IrH(COD)(PBn3){η2-P,C-(C6H4CH2)PBn2}]PF6 (4) are active in the transfer hydrogenation of ketones. However, complex (3) gives the best results in conversion toward the alcohol. Interestingly, commercial isopropanol was used as hydrogen source, without any drying treatment. In situ generated isopropoxide was used as base. An efficient conversion of a variety of ketones, aromatic or aliphatic, cyclic or linear, including molecules with conjugated or isolated C C moieties was achieved, thus reporting 12 examples of hydrogenated substrates. Ketones of higher steric hindrance could not be converted under the studied conditions. The experimental evidence indicates that the steric and electronic properties of the substrates are determinant in the observed conversions and performance of the system. For α,β-unsaturated ketones, preference toward the reduction of the C C bond was observed. However, the system shows chemoselectivity toward the carbonyl group in molecules which also bear an isolated C C moiety. With the results obtained, a pseudo first-order dependence of the reaction rate on the concentration of ketone was determined. Also, stoichiometric as well as in situ tests were performed to shed light into the reaction pathways possibly involved in the catalytic TH of ketones described herein (precursor 3, base and isopropyl alcohol as hydrogen source).

Chiral secondary alcohols are ubiquitous motifs in numerous natural products, pharmaceuticals, and biological active compounds. Catalytic asymmetric hydrogenation of multi-functionalized ketones provides an effective and powerful synthesis method to construct chiral secondary alcohols. In the asymmetric hydrogenation of multi-functionalized ketones, the simultaneous coordination of the carbonyl oxygen of ketones and adjacent functional groups to central metal of the catalyst is the key factor for the asymmetric induction. However, for ketones with two adjacent coordinating groups, the competitive ligation of the adjacent coordinating groups to central metal tends to decrease the enantioselectivities. In this review, we summarized the know how in achieving high chemo-, enantio-, and diastereoselectivities in asymmetric hydrogenation of multi-functionalized ketones, i.e. to change the bulkiness and/or electronic properties of the coordinating groups in substrates and in ligands, or to introduce a third coordinating ligand (solvent) to make one coordination much more stronger than the other.

Metal catalyzed reductive couplings of π-unsaturated reagents with carbonyl compounds via hydrogenation or transfer hydrogenation has emerged as an alternative to the use of stoichiometric organometallic reagents in carbonyl addition.

An inorganic-organic hybrid catalyst, Ru(II)Cym@PMOB, was synthesized by anchoring of [Ru(II)Cl2(p-cymene)]2 complex which is derived from a reaction between hydrated ruthenium(III) trichloride and α-phellandrene over aminofunctionalized benzene-organosilica (PMOB). In the context of secondary alcohol synthesis from ketones, transfer hydrogenation (TH) reactions are convenient compared to conventional hydrogenation reactions owing to its lower activation energy and ambient pressure and mild temperature reaction conditions. The synthesized catalysts were characterized by CHN analysis, XRD, ICP, N2-sorption analysis, TG & DTA, FTIR, 13C & 29Si solid NMR, UV–vis, TEM, SEM and XPS. The catalytic activities of neat [Ru(II)Cl2(p-cymene)]2 complex and Ru(II)Cym@PMOB were evaluated in transfer hydrogenation (TH) of ketones (∼97%) and compared with conventional hydrogenation reactions (∼5%) where molecular H2 was used. The results showed Ru(II)Cym@PMOB as highly active catalyst towards transfer hydrogenation (TH) reaction of acetophenones compared to neat [Ru(II)Cl2(p-cymene)]2 complex. The heterogeneity of Ru(II)Cym@PMOB was confirmed by Sheldon’s test.

The acetophenone (1a) reduction using catalytically active nickel complexes and water is an efficient and sustainable method to access a new methodology of transfer hydrogenation of ketones. When triethylsilane (Et3SiH) was used as sacrificial agent to promote the transfer hydrogenation from water, 1-phenylethanol (2a) was obtained in excellent yield along with silanol (Et3SiOH) as the reaction’s driving force. Deuterium labeling studies were made using Et3SiD or D2O and these studies showed that both compounds participate as hydride sources for the ketone reduction. A scope of substrates was assessed, including a variety of mono/diketones, and α,β-unsaturated ketones, to yield the corresponding secondary alcohols and saturated ketones. Additionally, asymmetric transfer hydrogenation of mono-ketones was studied for the mixture of nickel/(bisphosphine or phospholane) as catalyst precursor, using H2O/Et3SiO system and ethanol as hydrogen sources.

A stereoselective hydrogenation of 1,3-diynes with an air-stable copper(I)/N-heterocyclic carbene complex, [IPrCuOH], has been developed. The corresponding products, 1,3-dienes, are obtained in a stereoselective manner depending on their substitution pattern: Diaryl-diynes yield E,E-1,3-dienes, whereas dialkyl-diynes are converted to the corresponding Z,Z-1,3-dienes. Hydrogenation and deuteration experiments with enynes indicate that these are competent reaction intermediates in the hydrogenation of diynes.

The use of the complex [Ru3(CO)12] (1) as a catalyst precursor (0.1 mol%) at 200 °C, 60 psi of H2, along with triphenylphosphine (TPP) generated ruthenium nanoparticles (Ru-Nps); this occurred in the presence of pyridine-nitriles leading to a variety of hydrogenation (secondary amine, imine, or imidazole) products, depending of the pyridine-nitrile used, under similar reaction conditions. This relates to relatively good to modest yields, determined by the substituents in the corresponding pyridine. In sharp contrast, the use of aromatic dinitriles did not generate Ru-Nps at 140 °C, 150 psi of H2 and TPP, but allowed the homogeneous catalytic hydrogenation of the 1,4- and 1,3-dicyanobenzenes, to yield the corresponding CN-substituted secondary amine or imine. The main products were characterized by different analytical methods and spectroscopic techniques.

Herein, it is presented a novel catalytic system for the continuous-flow chemoselective hydrogenation of α,β – unsaturated aldehydes used in the production of high-value cosmetics and pharmaceuticals precursors. The reaction was catalyzed by nano-nickel particles grafted on polymeric support, synthesized via a simple, adaptable and green methodology. The system was highly active and very selective to C C bond saturation.

New cyclometalated ruthenium(II) complexes of the type [Ru(L)(CO)(EPh3)2] (L = di-anionic CNO- donor of 1-(biphenylazo)naphthol; E = P, As) have been synthesized by the reaction using [RuHCl(CO)(EPh3)3] (E = P, As) with 1-(biphenylazo)naphthol ligand (H2L). The 1-(biphenylazo)naphthol ligand and ruthenium complexes are characterized by analytical, spectral (FT–IR, UV–Vis, 1H NMR and 31P NMR) methods. The molecular structure of ruthenium complex 1 was further confirmed by single crystal X-ray diffraction method. The catalytic efficiency of ruthenium complex 1 was evaluated for the transfer hydrogenation of various ketones to alcohols with excellent conversion up to 99% in the presence of i-PrOH/KOH at 82 °C.

Herein, we report a catalyst composed of palladium nanoparticles immobilized on polymeric resin for chemoselective hydrogenation reactions under flow conditions. The catalyst exhibits high activity and selectivity towards hydrogenation of C C double bond, as confirmed in the hydrogenation of 2-heptene and 6-methyl-5-hepten-2-one.

An efficient catalytic system containing [RuCl2(η6-p-cymene)]2 and one P,N ligand, N-diphenylphosphino-2-aminopyridine (L1) was loaded in catalyzing the alkylation of ketones with primary alcohols for a diverse array of substrates. Other five P,N ligands based on pyridin-2-amine and pyrimidin-2-amine were also examined in this reaction to explore the influence of steric hindrance and electronic effects. Monitoring by 1H NMR and ESI-MS reveals a stable cationic L1-coordinated ruthenium hydride intermediate, identified as [Ru(η6-p-cymene)(κ2-L1)H]+. Organic intermediates consistent with a three-step dehydrogenation, alkylation and hydrogenation pathway were also observed. The final step in this reaction, the ruthenium-catalysed transfer hydrogenation reduction of α,β-unsaturated ketone with benzyl alcohol was performed separately.

Rates of C3-C5 ketone hydrogenation are measured in the vapor phase over Ru/SiO2. Reaction kinetics are considered through a range of ketone partial pressures (0.3–30 Torr), hydrogen partial pressures (90–900 Torr), and reaction temperatures (322–456 K). Ketone hydrogenation is observed to be facile, with site time yields ranging from 0.14 s−1 for 2-pentanone to 0.37 s−1 for acetone at 322 K and 1.2 bar H2. At low temperatures, apparent reaction orders and kinetic barriers are similar for all ketones. During acetone hydrogenation at higher temperatures, (422 K), the ketone order increases from 0 to 0.4, while the hydrogen order increases from 0.5 to 0.9. Furthermore, the apparent barrier decreases from ≈50 kJ mol−1 at 322 K to ≈18 kJ mol−1. Apparent trends in hydrogenation rates are interpreted at an elementary level using a microkinetic analysis that is based on a Horiuti-Polanyi mechanism involving two distinct surface sites.

This paper reports results of a comparative study of the structure and activity of MgF 2 -supported metal (Me) catalysts containing 1 wt.% of platinum, iridium or ruthenium. Their activities for hydrogenation of toluene and selective hydrogenation of ortho-chloronitrobenzene to ortho-chloroaniline were compared with the hydrogenation performance of metal catalysts prepared by impregnation of a alumina which is one of the most widely used supports. The catalysts were characterized by using low-temperature nitrogen adsorption, TPR-H 2 and H 2 -chemisorption techniques. The nature of metal and support appeared to have a clear influence on metallic phase dispersion and it was reflected by the activity of Me/MgF 2 catalysts. The application of magnesium fluoride as a support has enabled to obtain catalysts showing high activities for hydrogenation of toluene at 323–498 K and selective hydrogenation of ortho-chloronitrobenzene (o-CNB) to ortho-chloroaniline (o-CAN) in the liquid-phase at 353 K under hydrogen pressure of 4 MPa. From among the catalysts studied, the highest activity for the both aforementioned reactions has been found in the case of MgF 2 -supported platinum catalyst and the highest selectivity (100%) in that of ruthenium-containing catalyst. The activity of magnesium fluoride-supported catalysts was several times higher than that of alumina-supported ones.

New PHOX ligands, derived in three steps from (1R,2S,3R,5R)-3-amino-apopinan-2-ol 1 and (1R,2R,3S,5R)-3-amino-pinan-2-ol 2 were applied as chiral ligands for the formation of ruthenium catalysts. The catalysts were used in asymmetric transfer hydrogenations of prochiral ketones producing the corresponding alcohols in moderate to high yields and enantioselectivity.

A series of Ru(II)-benzene organometallic compounds (1–6) constructed from [RuCl2(η6-benzene)]2 and chiral aroylthiourea ligands (L1-L6) obtained from D/L-phenylalanine, was fully characterized. The chiral complexes along with 2-propanol and NaOH effected the asymmetric hydrogenation of aromatic ketones at 82 °C within 8–10 h. The reduction reactions proceeded with excellent conversions and enantiomeric excesses (up to 99%).

International audience; A catalytic hydrogenation of carbonyl derivs. with a manganese pre-catalyst has been developed. The key feature is the use of an air stable cationic manganese pre-catalyst bearing a tridendate ligand with a 2,6-(diaminopyridinyl)diphosphine scaffold. Under 50 bar of H2, at 130°, various ketones were reduced to the corresponding alcs. with moderate to good yield.

New ionic Schiff-base ligands have been synthesized by condensation of (3-formyl-4-hydroxybenzyl)triphenylphosphonium and 3-(3-formyl-4-hydroxybenzyl)-1-methyl-1H-imidazol-3-ium chloride and hexafluorophosphate salts with N,N-dimethylethylenediamine. Treatment of the dimeric derivative [{RuCl(μ-Cl)(η6-p-cymene)}2] with two equivalents of these ligands allowed the preparation of novel mononuclear water-soluble Ru(II) complexes, which proved to be catalytically active in the transfer hydrogenation of ketones and aldehydes under aqueous conditions.

Novel chiral multidentate P3N4-type ligand has been synthesized and characterized by NMR and HRMS. Using i-PrOH as solvent and hydrogen source, asymmetric transfer hydrogenation of various ketones was investigated. The catalyst generated in situ from chiral multidentate aminophosphine ligand (R,R,R,R)-3 and IrCl(CO)(PPh3)2 exhibited highly catalytic activity and excellent enantioselectivity under mild conditions, achieving the corresponding chiral alcohols with up to 99% yield and 99% ee.

Catalytic experiments were performed for the hydrogenation of o-cresol in n-dodecane over a platinum catalyst. Batch reactions analyzed with an in-situ ATR IR probe suggest that the hydrogenation results in the formation of the final product, 2-methyl-cyclohexanol, with 2-methyl-cyclohexanone as the intermediate product. Ab initio density-functional theory was employed to investigate the atomic-scale mechanism of o-cresol hydrogenation on the Pt(111) surface. The formation of 2-methyl-cyclohexanone was found to involve two steps. The first step is a hydrogen abstraction, that is, the H atom in the hydroxyl group migrates to the Pt surface. The second step is hydrogenation, that is, the pre-existing H atoms on Pt react with the carbon atoms in the aromatic ring. On the other hand, 2-methyl-cyclohexanonol may be produced through two paths, with activation energies slightly greater than that for the formation of 2-methyl-cyclohexanone. One path involves direct hydrogenation of the aromatic ring. Another path involves three steps, with the partial hydrogenation of the ring as the first step, hydrogen abstraction of the OH group as the second, and hydrogenation of remaining C atoms and the O atom the last.

A series of M/Mo2C (M = Cu, Pd, Co and Fe) were synthesized and evaluated for CO2 hydrogenation at 135–200 °C in liquid 1,4-dioxane solvent. The Mo2C served as both a support and a co-catalyst for CO2 hydrogenation, exhibiting turnover frequencies of 0.6 × 10−4 and 20 × 10−4 s−1 at 135 and 200 °C, respectively. Methanol was the major product at 135 °C, while CH3OH, C2H5OH, and C2+ hydrocarbons were produced at 200 °C. The addition of Cu and Pd onto the high surface area Mo2C enhanced the production of CH3OH, while Co and Fe enhanced the production of C2+ hydrocarbons. Results for CO2, CO, and CH3OH hydrogenation experiments suggested that CO2 was the primary source for CH3OH while CO was the intermediate to hydrocarbons during CO2 hydrogenation. Characterization of the spent M/Mo2C catalysts revealed very little change in the surface and bulk chemistries and structures, indicating their stability in the liquid environment.

A new catalyst containing metallic ruthenium nanoparticles intercalated in hectorite (nanoRu′@hectorite) was found to catalyze the reduction of quinoline and quinoline derivatives by NaBH4 in aqueous solution to give selectively the corresponding 1,2,3,4-tetrahydroquinolines (N-cycle hydrogenation). In most cases the reaction can be done under mild conditions (25–60 °C) without pressure equipment, conversion and selectivity being superior to 99%. In the case of sterically hindered derivatives, the reaction can be done in a pressure vessel under self-generated pressure (up to 9 bar). Isoquinoline and quinoxalines also undergo selective N-cycle hydrogenation, but 2-phenyl-quinoline is hydrogenated to give 2-phenyl-5,6,7,8-tetrahydroquinoline (C-cycle hydrogenation). Isotope labeling experiments combined with semi-empirical calculations of the electrostatic potentials support a heterolytic hydrogenation mechanism involving a hydride from NaBH4 and a proton from H2O. The catalyst nanoRu′@hectorite can be recycled and reused.

The new chiral aminomethyl quinazoline (amq) type ligand derived from L-phenylalanine was synthesized and coordinated with [RuCl2(PPh3) dppb] to obtain ruthenium(II) complex. This catalyst displayed considerable reactivity (up to 97% ee and 99% conversion) in the asymmetric transfer hydrogenation of ketones using 2-propanol as a hydrogen source in the presence of NaOiPr. (C) 2016 Elsevier B.V. All rights reserved.

The asymmetric reduction of prochiral ketones is a pivotal reaction for the preparation of chiral alcohols which form an extremely important class of intermediates for fine chemicals and pharmaceuticals. Especially, iridium-based asymmetric reduction of ketones to enantiomerically enriched alcohols has recently attracted important attention by a number of research groups and interest in this area is growing. Therefore, a series of novel neutral mononuclear iridium(III) ferrocenyl-phosphinite complexes have been prepared and applied in the iridium(III)-catalyzed asymmetric transfer hydrogenation (ATH) of ketones to give corresponding secondary alcohols with outstanding enantioselectivities and reactivities using 2-propanol as the hydrogen source (up to 99% ee and 99% conversion). It was seen that the substituents on the backbone of the ligands resulted in a significant effect on both the activity and % enantioselectivity. Furthermore, the structural elucidation of the complexes was carried out by elemental analysis, IR and multi-nuclear NMR spectroscopic data.

In this study we report the catalytic hydrogenation of biomass-derived condensation product of furfural and cyclopentanone (F2C) with molecular hydrogen and formic acid as a source of hydrogen. Supported palladium catalysts have been used for hydrogenation and decomposition of formic acid. Complete conversion of F2C and higher than 90% yield of C15 bis-cyclic ether were achieved over 5% Pd/C catalyst at mild reaction conditions and short reaction time by catalytic hydrogenation with molecular hydrogen. Despite high activity of palladium catalysts in F2C hydrogenation with molecular hydrogen and also decomposition of formic acid to hydrogen these catalysts exhibited significantly lower activity in transfer hydrogenation. A dramatic activity loss in transfer hydrogenation may be caused by a strong adsorption of formic acid on Pd sites which hinders the competitive adsorption of F2C molecules solvated with formic acid.

Synthesis of new air stable octahedral ruthenium(II) carbonyl complex bearing O, and N-bidentate benzhydrazone ligand is reported. It has been characterized by elemental analysis, spectral methods and single crystal X-ray diffraction method. The new catalyst has been effectively applied to the transfer hydrogenation reaction of various ketones using isopropanol as a solvent and KOH as a base at 82 °C and the maximum conversion is achieved up to 100%.

Deprotonation of HOC(CH2)5CH2C6H4–NMe2-2 (L1H) and HOC(CH2)5C6H4–NMe2-2 (L2H) by equivalent of n-BuLi afforded the pale yellow mixture L1Li or L2Li, which reacted with MgBr2 in different molar ratios to give three novel bidentate N, O-magnesium complexes (1), (2) and (3), respectively. Complexes 1–3 were characterized by 1H and 13C NMR spectroscopy, elemental analyses and single crystal X-ray diffraction techniques. Each of the complexes 1, 2 and 3 was tested for the capability of catalyzing transfer hydrogenation of ketones. Complex 1 exhibited good to excellent catalytic activity, while complexes 2 and 3 showed good activities for the transfer hydrogenation of ketones.

Six cationic ruthenium(II) arene thioamide complexes with the general molecular formula [Ru(η6-p-cymene)(PPh3)(L)]+ [where, L = pyridine-2-thioamide and its derivatives] have been successfully synthesized from the reaction of [Ru(η6-p-cymene)Cl2]2 with chelating thioamide ligands and PPh3 in methanol in 1:2 M ratio respectively. All the complexes were isolated as their BPh4−salts and were fully characterized by analytical and spectral (FT-IR, UV-Vis and1H-NMR) methods. The solid-state structure of one of the complexes, [Ru(η6-p-cymene)(PPh3)(L4)]BPh4 (4) (L4 = N-(2, 4, 6-Trimethylphenyl)pyridine-2-thiocarboxamide) has been established by X-ray single crystal diffraction which indicates a pseudo-octahedral (piano-stool) coordination geometry is present in the complex. The ruthenium(II) complexes have been examined for the transfer hydrogenation of various aromatic, heterocycle and cyclic ketones. The formation of ruthenium(II) hydride is confirmed by 1H- NMR and is proposed as the catalytic intermediate in this reaction. Under the optimized conditions, these ruthenium complexes served as excellent catalyst precursors which smoothly reduce the ketones with conversion up to 100%. The influence of other variables on the transfer hydrogenation reaction such as solvent, base, temperature, time, catalyst loading and substrate scope is also reported. Furthermore, the catalyst could be easily recovered and reused at least three times without obvious loss of conversions.

This paper presents the first systematic thermodynamic study of the vapour phase transfer hydrogenation of α,β-unsaturated carbonyl compounds at temperatures: 423.15–723.15 K. Calculations were made for four compounds, namely: acrolein, α-methylacrolein, β-methylacrolein and methyl vinyl ketone. The Gibbs free energies and equilibrium mole fractions (EMFs) were calculated for transfer hydrogenation with ethanol and 2-propanol as hydrogen donors. It was noted that for transfer hydrogenation and hydrogenation with hydrogen the formation of the unsaturated alcohol (UOL) is the least thermodynamically favoured reaction and that saturated alcohol (SOL) and saturated aldehyde or ketone (SAL or SON) are the main products. A set of eight carbonyl compounds have been transfer hydrogenated with ethanol and 2-propanol in the presence of MgO as the catalyst. The main conclusions are that: (a) the reduction of a carbonyl group into a carbinol group occurs with a very high selectivity, (b) for almost all carbonyl compounds, except acrolein, the reactivity of 2-propanol highly exceeded that shown by ethanol and (c) the high chemoselectivity of transfer hydrogenation of acrolein with alcohols resulted from the kinetic control caused by the presence of magnesium oxide.

Asymmetric hydrogenation of 4-substituted cyclic enamido esters catalyzed by a rhodium–TangPhos complex provides an efficient method for the synthesis of chiral 4-substituted oxazolinones with excellent yields and good enantioselectivities. The products are valuable chiral building blocks and the applications as chiral auxiliaries and pharmaceuticals are well-known.

The liquid-phase hydrogenation of aromatic trinitro compounds was studied at atmospheric and elevated pressure and a temperature of 50–70 °C. It was shown that at atmospheric pressure, irrespective of the solvent type (water or acetic anhydride), a complete reduction of the nitro groups of 2,4,6-trinitrobenzoic acid to amino groups does not occur; the intermediate products of hydrogenation and the products of secondary transformations are present in the solution. An increase in pressure to 5 bars ensures a complete hydrogenation of 2,4,6-trinitrobenzoic acid and 1,3,5-trinitrobenzene with the formation of 1,3,5-triaminobenzene.

This digest Letter comprises recent advances in the synthesis of chiral building blocks that uses rhodium catalyzed asymmetric hydrogenation of olefins. The first part of this revision covers the examples that have broadened the scope of the hydrogenation of enamides and enol esters. The second part focuses on the hydrogenation of alternative classes of substrates like unsaturated carboxylic acids, nitroderivatives or phosphonates among others. Overall, the diversity of structures and functional groups of substrates, along with the outstanding levels of catalyst efficiency shown in these contributions, have further established this reaction as a most valuable tool in asymmetric synthesis.

The rate and, more importantly, selectivity (ketone vs aromatic ring) of the hydrogenation of 4-phenyl-2-butanone over a Pt/TiO2 catalyst have been shown to vary with solvent. In this study, a fundamental kinetic model for this multi-phase reaction has been developed incorporating statistical analysis methods to strengthen the foundations of mechanistically sound kinetic models.A 2-site model was determined to be most appropriate, describing aromatic hydrogenation (postulated to be over a platinum site) and ketone hydrogenation (postulated to be at the platinum–titania interface). Solvent choice has little impact on the ketone hydrogenation rate constant but strongly impacts aromatic hydrogenation due to solvent-catalyst interaction. Reaction selectivity is also correlated to a fitted product adsorption constant parameter. The kinetic analysis method shown has demonstrated the role of solvents in influencing reactant adsorption and reaction selectivity.

Gas-phase hydrogenation of a wide range of ketones to alkanes, including hydrogenation of aliphatic ketones and acetophenone, was investigated using bifunctional metal–acid catalysis. The catalysts were comprised of a metal (Pt, Ru, Ni, and Cu) supported on acidic caesium salt of tungstophosphoric heteropoly acid Cs2.5H0.5PW12O40 (CsPW). The reaction occurred via a sequence of steps involving hydrogenation of ketone to alcohol on metal sites followed by dehydration of alcohol to alkene on acid sites and finally hydrogenation of alkene to alkane on metal sites. Catalyst activity decreased in the order: Pt > Ru >> Ni > Cu. Pt/CsPW showed the highest catalytic activity, giving almost 100% alkane yield at 100 °C and 1 bar pressure. Evidence is provided that the reaction with Pt/CsPW at 100 °C is limited by ketone-to-alcohol hydrogenation, whereas at lower temperatures (≤60 °C) by alcohol dehydration yielding alcohol as the main product. The catalyst comprised of a physical mixture of Pt/C + CsPW was found to be highly efficient as well, which indicates that the reaction is not limited by migration of intermediates between metal and acid sites in the bifunctional catalyst.

In this review, we consider the main processes for the asymmetric transfer hydrogenation of ketones from 2008 up today. The most effective organometallic compounds (derived from Ru, Rh, Ir, Fe, Os, Ni, Co, and Re) and chiral ligands (derived from amino alcohols, diamines, sulfur- and phosphorus-containing compounds, as well as heterocyclic systems) will be shown paying special attention to functionalized substrates, tandem reactions, processes under non-conventional conditions, supported catalysts, dynamic kinetic resolutions, the use of water as a green solvent, theoretical and experimental studies on reaction mechanisms, enzymatic processes, and finally applications to the total synthesis of biologically active organic molecules. We thank the continuous financial support from our Ministerio de Ciencia e Innovación (MICINN) (projects CTQ2007-62771/BQU, CTQ2010-20387, CONSOLIDER INGENIO 2010-CDS2007-00006, CTQ2011-24151, CTQ2011-24165), the Ministerio de Economía y Competitividad (MINECO) (projects CTQ2013-43446-P, CTQ2014-51912-REDC, CTQ2014-53695-P), FEDER, the Generalitat Valenciana (PROMETEO 2009/039, PROMETEOII/2014/017), and the University of Alicante.

A sulfonated chiral diamine ligand anion-based functionalized ionic liquid has been synthesized. Then the new ionic liquid-regulating ruthenium complexes were prepared successfully and employed as efficient catalysts for the asymmetric transfer hydrogenation of various ketones. The catalysts were highly efficient for the hydrogenation of a wide range of substrates bearing different functional groups and could be separated easily from the reaction mixture by thermoregulated phase separation, which can be efficiently recycled five times without significant changes in catalytic activity and enantioselectivity.

In this article we highlight some of the recent developments in the aqueous-phase hydrogenation of alkenes and arenes. The traditional types of water-soluble catalysts applied in aqueous media are outlined together with recent trends towards the development of transition metal nanoparticle and nanocomposite catalysts. In addition, we describe some palladium nanoparticle catalysts that are stabilized by ionic polymers, which demonstrate superior activities in the aqueous-phase catalytic hydrogenation of styrene, used as a model substrate, compared to related palladium nanoparticles.

Hydrogenation of carbazole and N-ethylcarbazole over Raney-Ni catalyst were realized in the temperature range of 393–503 K. 4[H] adduct dominated the hydrogenation products and the formation of 2[H] adduct was the rate-limiting step during the period, in which the conversion of carbazole was less than 40%. The hydrogenation process followed pseudo-first-order kinetics and the hydrogenation activation energies of carbazole and N-ethylcarbazole were 90 kJ/mol and 115 kJ/mol, respectively. The reaction starting position as well as the pathway of the hydrogenation of (N-ethyl)carbazole were investigated by comparing the kinetic characteristics of hydrogen uptake of carbazole and N-ethylcarbazole. The results showed that the reaction was a stepwise hydrogenation process and the first H 2 was added to the C1 = C10 double bond in the hydrogenation.

A new Rh(III) complex containing the TsDPEN ligand and an η6-arene connected through a carbon tether is reported. The asymmetric transfer hydrogenation of a series of ketones catalyzed by this complex using the formic acid/triethylamine system provided the corresponding alcohols with complete conversions and a high level of enantioselectivity.

Catalytic reduction of aromatic ketones is an interesting reaction that leads to the obtaining of alcohols. Some of these alcohols are employed as intermediaries to produce chemical fine compounds. The bimetallic catalysts are widely used in the chemoselective hydrogenation. The Surface Organometallic Chemistry on Metals (SOMC/M) is a methodology employed to obtain bimetallic systems. In the present work the hydrogenation of ketones derived from acetophenone has been studied. The aim was observe the effect on activity and selectivity to aromatic alcohols by the presence of substituents in the ring. The chemical characteristics of substituents groups could influence the way aromatic ketones are absorbed on the metallic surface. This fact can be explained by a combination of geometric and electronic effects.

A series of the supported nickel catalysts have been synthesized through impregnation, characterized by X-ray diffraction, N 2 sorption measurement, temperature programmed H 2 reduction and X-ray photoelectron spectroscopy. The morphology and particle size of catalysts are imaged by scanning electron microscope. The catalysts have efficiently catalyzed the one-step hydrogenation of 1,5-dinitronaphthalene to 1,5-diaminodecahydronaphthalene. The catalyst 10%Ni/SiO 2 -1a is the most active for the titled hydrogenation with 100 mol% conversion and 95.3% selectivity, applicable for the catalytic one-step hydrogenation of nitro-aromatic compounds. The reducibility of NiO species on different supports has been carefully studied. Some factors such as the type of carriers, the addition of modifiers, the silica source, the Ni loading, the H 2 pressure and the reaction temperature and time play important roles in controlling the hydrogenation. In addition, the negative effect of the water amount has been observed. The recycling tests reveal the recyclability and stability of the supported Ni catalyst.

In this report, poly[acrylic acid] gels containing Al2O3 were prepared by simultaneous free-radical polymerization and sol–gel chemistry using different amounts of 3-(trimethoxysilyl)propyl methacrylate (TMPM) as a compatibilizer. The hybrid materials were used as supports for a rhodium catalyst in the chemoselective hydrogenation of 3-substituted aromatic nitro-compounds. The supported rhodium catalyst was prepared by an ion-exchange process. In situ H2 flux was used to produce active species of the catalysts. The resulting materials were characterized by infrared spectroscopy, thermogravimetric analysis, solid-state 29Si and 13C NMR, X-ray diffraction, transmission/scanning electron microscopy, and X-ray photoelectron spectroscopy. All materials exhibited simultaneous interpenetrating hybrid network structures (SIHNs). The morphologies and physicochemical properties depended on the amount of TMPM used. The catalysts were found to be effective for the reduction of nitrobenzene in ethanol at room temperature and a hydrogen pressure of 20 atm. The most active and selective catalyst was used in the hydrogenation of different 3-substituted aromatic nitro-compounds. The hydrogenation reactions displayed high conversion levels and promoted exclusive –NO2 group reduction, resulting in the sole formation of the corresponding amino-compound, with the exception of 1,3-dinitrobenzene, in which over-hydrogenation was detected. The presence of electron-donating/electron-withdrawing substituents at the 3-position resulted in different rates of –NO2group hydrogenation. This effect was quantified in terms of the Hammett relationship, in which the catalyst displayed a linear correlation between the substituent constant (σi) and the hydrogenation rate, with the exception of –OH, –NH2, and –OCH3 groups. One explanation for this behavior is a proposed support-substrate hydrogen bond interaction during the catalytic reaction., The authors thank FONDECYT (grant no. 1110079), FONDECYT (grant no. 1100259), REDOC (MINEDUC Project UCO1202 at U. de Concepción). B.F. Urbano thanks to FONDECYT Initiation (grant no. 11121291) and CIPA CONICYT Regional Project R08C1002. C.H. Campos thanks CONICYT and BECAS CHILE for a postdoctoral fellowship. We also acknowledge the generous support of the National Science Foundation (USA, ER, CHE1049569)

Asymmetric hydrogenation of 1-silyl-1-substituted alkenes has been explored, producing eight optically active silanes with good to excellent enantioselectivity (66–99% ee) and yield (74–99%). The reaction was efficiently catalyzed by the cationic N,P-Ir complexes, and the polar solvents were found to be essential for the stereocontrol of the conversion.

With benzaldehyde as a model compound, the hydrogenation of aromatic aldehydes to aromatic hydrocarbons was investigated. Cu-HZSM-5 exhibited excellent catalytic performance for the reaction. The obtained catalysts were characterized by N 2 adsorption/desorption, N 2 O chemisorptions, X-ray diffraction, NH 3 -temperature programmed desorption and X-ray photoelectron spectroscopy. It was found that Cu 0 active species exhibited poor activity for the hydrogenation of benzene ring, while the strong acidity of HZSM-5 accelerated the hydrogenation reaction via hydrogen spillover phenomenon and the C–O activation effect. In addition, the catalyst was proved to be effective for the hydrogenation of a series of aromatic aldehydes to corresponding aromatic hydrocarbons.

An imidazolium ion tethered TsDPEN has been synthesized readily and used as a water-soluble ligand for [Cp*RhCl2]2 catalyzed asymmetric transfer hydrogenation (ATH) of aromatic ketones in water. This process provided the secondary alcohols in moderate to excellent conversions (up to 100%) with high enantioselectivities (up to 98% ee) under mild reaction conditions without adding any surfactants. The catalytic system is highly effective with the substrate to catalyst (S/C) ratio of 500 and low hydride donor loading of 1.5 equiv. of HCO2Na. The procedure presented is simple and makes this method suitable for practical use.

New 4-acetylbenzyl-N-heterocyclic carbene ligands (1–4) have been used to synthesize iridium complexes 6–9 and ruthenium complex 10. All complexes were characterized by FT-IR, 1H and 13C NMR spectroscopy, elemental analysis, and in the case of 6, by X-ray diffraction studies. The catalytic performance of these iridium and ruthenium complexes for transfer hydrogenation of ketones and imines and N-alkylation of amines with primary alcohols were tested in a range of substrates, and showed high catalytic activity with 1 mol% catalytic loading. The neutral complex 8 with two acetyl groups also showed good catalytic efficiency under lower catalyst loading (0.01 mol%), with the maximum TON of 8000, while on the other hand, the cationic complex 9 with PF6− as counteranion showed good to excellent catalytic activity toward the N-alkylation of amines in a wide scope of substrates. We also found out that the Ir complex 6′ was formed through the intramolecular C H activition of 6 under the transfer hydrogenation conditions.

Only four types of dimeric precursors [RuCl2(η6-arene)]2 for the synthesis of Noyori’s half sandwich diamine catalysts [RuCl(TsDPEN)(η6-arene)] are commercially available, yet so far no study has tried to systematically evaluate how these systems perform during the asymmetric transfer hydrogenation of various 3,4-dihydroisoquinolines (i.e., the typical substrates for Noyori asymmetric transfer hydrogenation benchmarking). Experiments combined with molecular modeling allowed us to assess their properties and formulate a hypothesis clarifying the difference in enantioselectivity of these systems.

The manuscript herein is on the synthesis and characterization of a graphene composite abbreviated as GO-IL-Ru that is based on graphite oxide with additional functional groups of organic ionic trains. It contains Ru at 1.61 wt% level (by ICP-OES). We have used GO-IL-Ru as catalyst in both the hydrogenation reactions and the transfer hydrogenation reactions. The catalytic activity of GO-IL-Ru was good at compounds with phenyl groups, but not at those containing electronegative substituents or heterocyclic rings.

A triphenylphosphine-stabilized Ir/SiO 2 catalyst modified by a chiral diamine was synthesized with four silica spheres as support for the asymmetric hydrogenation of aromatic ketones. The H-bond between substrate and silanols and the interaction between substrate and modifier commonly affected the steric configuration of asymmetric hydrogenation of aromatic ketones. With the silanols increasing, the activity of asymmetric hydrogenation significantly increased. This is the first report of heterogeneous asymmetric hydrogenation of aromatic ketones enhanced by silanols on highly monodispersed silica spheres with > 99.9% ee and > 99% conversion.

Ruthenium encapsulated in an aluminium oxyhydroxide-support was investigated for the transfer hydrogenation of aldehydes and ketones with potassium formate as a sustainable green hydrogen donor. The entrapped ruthenium were narrowly distributed with mean diameters of 1.5–1.8 nm. XPS studies show that the ruthenium was present as Ru 0 and Ru 3+ . The catalysts showed high activity even at low metal loadings of 0.5–2 wt.%. The maximum TOF for benzaldehyde hydrogenation was over 1 wt.% Ru. The reduction of aromatic and aliphatic aldehydes was facile and occurred with 100% yield. In comparison, ketones were less readily reduced although moderate to excellent yields could be obtained after a longer reaction time. No leaching of ruthenium was observed in contrast to a catalyst prepared by wet impregnation. Washing of the used catalyst with water and ethanol effectively removed the deposited bicarbonate co-product and the recycled catalyst maintained its activity up to five runs.