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As an extension of the reaction mechanism describing the base-catalyzed hydrogenation of ketones according to Berkessel et al., we use a standard methodology for transition-state (TS) calculations in order to check the possibility of heterolytic cleavage of H2 at the ketone's carbonyl carbon atom, yielding one-step hydrogenation path with involvement of carboxylic acid as a catalyst. As an extension of the catalyst scope in the base-catalyzed hydrogenation of ketones, our mechanism involves a molecule with a labile proton and a Lewis basic oxygen atom as a catalyst-for example, R-C(=O)OH carboxylic acids-so that the heterolytic cleavage of H2 could take place between the Lewis basic oxygen atom of a carboxylic acid and the electrophilic (Lewis acidic) carbonyl carbon of a ketone/aldehyde. According to our TS calculations, protonation of a ketone/aldehyde by a proton shuttle (hydrogen bond) facilitates the hydride-type attack on the ketone's carbonyl carbon atom in the process of the heterolytic cleavage of H2 . Ketones with electron-rich and electron-withdrawing substituents in combination with a few carboxylic and amino acids-in total, 41 substrate-catalyst couples-have been computationally evaluated in this article and the calculated reaction barriers are encouragingly moderate for many of the considered substrate-catalyst couples.

This paper presented a study on the role of yttrium addition to Ru-based catalysts for liquid phase paranitrotoluene hydrogenation reaction. An impregnation-precipitation method was used for preparation of a series of yttrium doped Ru/NaY catalysts with yttrium content in the range of 0.0026-0.0052 g/g. Properties of the obtained samples were characterized and analyzed by X-ray diffraction (XRD), H-2-TPR, Transmission electron microscopy (TEM), ICP atomic emission spectroscopy, and Nitrogen adsorption-desorption. The results revealed that catalytic activity of NaY supported Ru catalysts increased with the yttrium content at first, then decreased with the further increase of yttrium content. When yttrium content was 0.0033 g/g, a Ru-Y/NaY2 catalyst showed the most excellent performance of paranitrotoluene hydrogenation reaction (paranitrotoluene conversion and the selectivity toward P-methyl-cyclohexylamine reached 99.9% and 82.5%, respectively). In addition, to compare with the performance of Ru-Y/NaY catalysts, the active carbon supported Ru catalysts were prepared using the same method in view of its higher surface area and adsorption capacity. Finally, the effect of solvent on the reaction over Ru-Y/NaY2 catalyst has been investigated, it was found that the best performance of paranitrotoluene hydrogenation reaction took place in protic solvents (isopropanol and ethanol). This was mainly ascribed to their polarity and hydrogen-bond accepting capability.

We report carbon can be activated as metal-like hydrogenation catalyst for selective hydrogenation of nitroarenes. Using DFT calculations we demonstrated the combination of P-dopant and lattice defect in carbon can cause significant electron delocalization and change the band structure as metal-like one, and thus both H2 and nitro group are easily activated for selective hydrogenation. Then we fabricated this carbon catalyst with tunable concentration of P-dopant and lattice defect by polymerization and carbonization of phytic acid, and found the concentration of lattice defect is closely related to that of P-dopants. The synthesized catalyst exhibits superior catalytic activity, perfect selectivity and stability in the hydrogenation of nitroarenes, outperforming the reported metal-free, metal-oxide and nickel catalysts. Importantly, the hydrogenation activity is linearly dependent on the P-doping and/or defect concentration, perfectly agreeing with the DFT calculation. This work is expected to provide a cheap way for large-scale production of anilines using metal-like carbon catalyst.

A series of bulky pyridine-bridged NHC-Ru complexes have been rationally designed and synthesized; these exhibited very high catalytic activity in the hydrogenation of cyclic and linear carbonates under mild reaction conditions. In the presence of catalytic amounts of a weak base, a broad range of substrates with different ring size and steric bulk were well tolerated, providing methanol and the corresponding diols in excellent yields with a catalyst loading as low as 0.5 mol %.

Herein, we report a heterogeneous TiO2-supported Re catalyst (Re/TiO2) that promotes various selective hydrogenation reactions, e.g. hydrogenation of esters to alcohols, hydrogenation of amides to amines, and N-methylation of amines using H2 and CO2. Initially, Re/TiO2 was evaluated in the context of the selective hydrogenation of 3-phenylpropionic acid methyl ester to afford 3-phenylpropanol (pH2 = 5 MPa, T = 180 oC), where revealed a superior performance relative to other catalysts explored in this study. In contrast to other typical heterogeneous catalysts, Re/TiO2 did not produce dearomatized byproducts. DFT studies suggested that the high selectivity for the formation of alcohols in favor of the hydrogenation of aromatic rings, should be ascribed to the higher affinity of Re toward the -COOCH3 group relative to the benzene ring. Re/TiO2 is moreover recyclable and shows a wide substrate scope for the reaction (19 examples). Subsequently, Re/TiO2 was applied to the hydrogenation of amides and the N-methylation of amines with H2 and CO2. Furthermore, Re/TiO2 promotes the N-alkylation of amines with carboxylic acids or esters in the presence of H2.

Selective hydrogenation reaction over supported metal nanoparticles (NPs) through activation of molecular H2 is very demanding in the context of maintaining atom efficiency in chemical reactions. Although high selectivity is difficult to achieve in the reaction, but it is very challenging. In this research, we separately deposited Pd and Pt NPs on nanoporous hollow polymer tubes (PP-3) and studied their efficiency in hydrogenation of α,β-unsaturated aldehydes as substrates. We found hydrogenation selectivity over these two types of catalysts (Pd@PP-3 and Pt@PP-3) were entirely different. Pt@PP-3 shows high selectivity in the hydrogenation of C=O bonds, producing unsaturated alcohol in high yield, whereas Pd@PP-3 only hydrogenates C=C bonds and forms saturated aldehyde as the major product. Pd@PP-3 and Pt@PP-3 were thoroughly characterized by PXRD, N2 sorption, TEM, XPS, CO stripping experiment and in-situ CO adsorption FT-IR studies. Our research implies the utility of porous organic polymers as support for metal NPs mediated hydrogenation reactions.

The hydride isonitrile complex [FeH(CNCEt3)(1a)]BF4 (2) containing a chiral P2(NH)2 macrocycle (1a), in the presence of 2-propanol as hydrogen donor, catalyzes the base-free asymmetric transfer hydrogenation (ATH) of prostereogenic ketones to alcohols and the hemihydrogenation of benzils to benzoins, which contain a base-labile stereocenter. Benzoins are formed in up to 83% isolated yield with enantioselectivity reaching 95% ee. Ketones give the same enantioselectivity observed with the parent catalytic system [Fe(CNCEt3)2(1a)] (3a) that operates with added NaOtBu

A new chiral manganese PNP pincer complex is described. The asymmetric hydrogenation of several prochiral ketones with molecular hydrogen in the presence of this complex proceeds under mild conditions (30-40 °C, 4 h, 30 bar H2 ). Besides high catalytic activity for aromatic substrates, aliphatic ketones are hydrogenated with remarkable selectivity (e.r. up to 92:8). DFT calculations support an outer sphere hydrogenation mechanism as well as the experimentally determined stereochemistry.

We successfully developed asymmetric hydrogenation of β-silyl-α,β-unsaturated esters to prepare chiral 3-substituted-3-silylpropionic ester products catalyzed by rhodium/bisphosphine-thiourea (ZhaoPhos) with excellent results (up to 97% yield, >99% ee, 1 500 TON). Moreover, our hydrogenation product can be efficiently converted to other important organic molecules, such as chiral ethyl (R)-3-hydroxy-3-phenylpropanoate, (R)-3-(dimethyl(phenyl)silyl)-3-phenylpropanoic acid.

A simple and efficient method for determination of the yield, enantiomeric/diasteriomeric excess (ee/de), and absolute configuration of crude chiral diols without the need of work-up and product isolation in a high throughput setting is described. This approach utilizes a self-assembled iminoboronate ester formed as a product by dynamic covalent self-assembly of a chiral diol with an enantiopure fluorescent amine such as tryptophan methyl ester or tryptophanol and 2-formylphenylboronic acid. The resulting diastereomeric boronates display different photophysical properties and allow for fluorescence-based ee determination of molecules containing a 1,2- or 1,3-diol moiety. This method has been utilized for the screening of ee in a number of chiral diols including atorvastatin, a statin used for the treatment of hypercholesterolemia. Noyori asymmetric hydrogenation of benzil was performed in a highly parallel fashion with errors

Double asymmetric hydrogenation of linear β,β-disubstituted α,β-unsaturated ketones catalyzed by the DM-SEGPHOS/DMAPEN/RuII complex with t-C4H9OK afforded the γ-substituted secondary alcohols in high diastereo- and enantioselectivities. Some mechanistic experiments suggested that two different reactive species, type (I) and (II), were reversibly formed in this catalytic system: Type (I) with the diamine ligand DMAPEN enantioselectively hydrogenated the enones into the chiral allylic alcohols, and type (II) without the diamine ligand diastereoselectively hydrogenated the allylic alcohols into the γ-substituted secondary alcohols. This dual catalysis protocol was successfully applied to the reaction of a variety of aliphatic- and aromatic-substituted enone substrates.

The Trost ligand, (1S,2S)-1,2-diaminocyclohexane-N,N′-bis(2′-diphenylphosphinobenzoyl) (L), is reported for the first time as a ligand for the asymmetric hydrogenation (AH) of ketones. Ligand (S,S)-L was screened in the presence of several metal salts and was found to form active catalysts if combined with ruthenium sources in the presence of hydrogen and a base. Reaction optimization was performed by screening different Ru sources, solvents, and bases. Under the optimized conditions, the complex formed by the combination of (S,S)-L with RuCl3(H2O)x in the presence of Na2CO3 was able to promote the AH of several ketones at room temperature in good yields with up to 96 % ee. The reaction kinetics measured under the optimized conditions revealed the presence of a long induction period, during which the initially formed Ru species was transformed into the catalytically active complex by reaction with hydrogen. Remarkably, a ketone that is a precursor of the antiemetic drug aprepitant was hydrogenated in excellent yield with a good ee value.

Base-metal catalysis, especially with non-noble-metal pincer-type catalysts, is increasingly used in organic synthesis and thus becoming more and more important for organometallic chemistry. After ruthenium-, iridium- and iron-based pincer-type complexes became established as state-of-the-art catalysts for (de)hydrogenation reactions in the past decade, manganese complexes have most recently been successfully applied in related transformations. Specifically, this microreview covers their recent progress in (de)hydrogenation and transfer (de)hydrogenation as well as in C–C and C–X bond-forming reactions.

A changeable ligand, which involves in activation of a catalyst or assists a reaction, draws an increasing attention, in contrast to a classical ligand as spectator. Proton-responsive catalysts, which are capable of undergoing changes of properties on gaining/losing one or more protons, provides interesting features as follows: (i) catalyst activation by electronic effect, (ii) pH-tuning of water-solubility, and (iii) second-coordination-sphere interaction. On the basis of this catalyst design concept, we developed several highly efficient proton-responsive catalysts for CO2 hydrogenation as H2 storage, formic acid (FA) dehydrogenation as H2 production, and transfer hydrogenation. The transformable ligands of proton-responsive catalysts in promoting effective catalysis have aroused our interest. In this account, we summarize our efforts for the development and application of proton-responsive catalysts. Specifically, the important role of pH-dependent proton-responsive complexes will be discussed.

We describe a tandem process to generate active Ru nanoparticles (≈7 nm) immobilised in situ on carbon from an organometallic precursor and formic acid to afford the hydrogenation of a wide range of arenes and heteroarenes in yields up to 72 % with high conversions and selectivities for the desired products. The hydrogenation of several substrates analogous to lignin-derived fragments to the corresponding alicyclic products was also achieved. Our experimental investigations evidenced that the observed enhanced activity for arene hydrogenation was driven by the unique structural advantages of the organometallic precursor to activate formic acid, in which the presence of a nitrogen ligand is crucial to achieve a high catalytic activity. TEM analysis revealed the formation of Ru0 nanoparticles, and Hg0 poisoning experiments support the heterogeneous nature of the active catalyst.

Two different iridium catalyst systems, generated from the ruthenocene-based phosphine-oxazoline ligand tBu-mono-RuPHOX or the diphosphine ligand BINAP, were developed for the asymmetric hydrogenation of 5,6-dihydropyrazin-2(1H)-ones, affording chiral piperazin-2-ones in good yields and with moderate to good ees. Different catalytic behaviors for the hydrogenation of these types of substrate were observed with these two catalyst systems. Our tBu-mono-RuPHOX ligand, which bears a ruthenocene scaffold with planar chirality, was found to be the best ligand for the [Ir(L)(COD)]BArF catalyst system, affording the desired products with up to 94% ee.

Manganese complexes of the types [Mn(PNP′)(Br)(CO)2] and [Mn(PNP′)(H)(CO)2] containing a tridentate ligand with a planar chiral ferrocene and a centro chiral aliphatic unit were synthesized, characterized, and tested in the enantioselective transfer hydrogenations of 13 ketones. The catalytic reactions proceeded with conversions up to 96 % and ee values up to 86 %. The absolute configuration of all products was determined to be (S). Notably, the presence of dihydrogen (up to 20 bar) did not affect the reduction. On the basis of DFT calculations, preliminary mechanistic details including the origin of the (S) selectivity are presented. The molecular structure of [Mn(PNP′)(Br)(CO)2] was studied by X-ray diffraction.

A series of phenanthroline based NHC and pyridine containing NNC and NNN pincer Ru(II) complexes were synthesized and fully characterized by various spectroscopic techniques. Comparative studies revealed that Ru(II)-NHC complexes were much more active than the Ru(II)-NNN complexes in both transfer hydrogenation (TH) of ketones and nitroarenes. Wingtip groups and counter anions modulated the impact of NHC complexes in both the reactions. The complexes with PF6- counter anion were found to be more active in TH of ketones while complexes with Cl- counter anion were superior towards the nitroarenes reduction. To the best of our knowledge this is the first example of counter anion controlled reactivity alteration between TH of ketones and nitroarenes.

The catalytic hydrogenation of nitriles to primary amines constitutes an environmentally benign and atom-economical methodology in synthetic organic chemistry. However, selective hydrogenation can be challenging, and usually elevated pressure and the use of various additives is requited. Herein the hydrogenation of aromatic and aliphatic nitriles to form primary amines catalyzed by ruthenium pincer complexes is described. The reactions are conducted at low H2 pressure, low catalytic loadings and, in case of a variety of benzonitriles, under neutral conditions and without any additives. Mechanistic insight is provided.

A modular ligand library of -amino acid hydroxyamides and thioamides was prepared from 10 different N-tert-butyloxycarbonyl-protected -amino acids and three different amino alcohols derived from 2, ...

A ferrocenyl-benzo-fused imidazolylidene complex of RuII was prepared and fully characterized. In the presence of acetylferrocenium tetrafluoroborate this complex can be oxidized to generate a complex with a cationic ligand. The neutral complex can be recovered by reducing the oxidized cationic compound with cobaltocene. The activity of the neutral and oxidized complexes was tested in the transfer hydrogenation of ketones and imines, using isopropyl alcohol as the hydrogen source. The neutral complex is very active in the reduction of all tested substrates, whereas the oxidized species shows low activity in the reduction of ketones. The rate of the reduction of hexaphenone could be modulated by addition of subsequent amounts of oxidant and reductant. The addition of acetylferrocenium tetrafluoroborate caused a decrease in the catalytic activity, whereas the addition of cobaltocene restored the activity. The catalytic activity shown by both catalysts in the reduction of N-benzylideneaniline was similar.

The methylenation/hydrogenation cascade reaction of aldehydes or ketones through a domino process involving two ensuing steps in a single pot is realized. The compatibility of Matsubara's reagent and Wilkinson's complex give a combination that allows, under dihydrogen, the transformation of a carbonyl function into a methyl group. This new method is suitable to introduce an ethyl motif from aromatic and aliphatic aldehydes with total chemoselectivity and total retention of α-stereochemical purity. The developed procedure is also extended to the introduction of methyl groups from ketones.

International audience; The first efficient and general rhenium-catalyzed hydrogenation of carbonyl derivatives was developed. The key to the success of the reaction was the use of a well-defined rhenium complex bearing a tridentate diphosphinoamino ligand as the catalyst (0.5 mol %) at 70 °C in the presence of H2 (30 bar). The mechanism of the reaction was investigated by DFT(PBE0-D3) calculations.

For the first time an easily accessible and well-defined manganese N,N,N-pincer complex catalyzes the transfer hydrogenation of a broad range of ketones with good to excellent yields. This cheap earth abundant-metal based catalyst provides access to useful secondary alcohols without the need of hydrogen gas. Preliminary investigations to explore the mechanism of this transformation are also reported.

Six quinazoline ligands (i.e., 3–8) were synthesized by starting from vasicine and vasicinone, and their applications towards ruthenium-catalyzed transfer hydrogenation reactions were evaluated. The 3/[RuCl2(p-cymene)]2 catalytic system was assessed for its use in the ruthenium-catalyzed transfer hydrogenation reaction of aldehydes, ketones, and imines to give the corresponding alcohols and amines and also assessed for its use in the direct reductive amination of carbonyl compounds with anilines. The 3/[RuCl2(p-cymene)]2 catalytic system demonstrated good to excellent activity in water with sodium formate as the hydrogen source. Current studies have revealed that among all of the synthesized ligands, those that have secondary amine groups and a rigid backbone are more active towards transfer hydrogenation reactions of unsaturated compounds.

Over the last few decades, the development of new and highly efficient synthetic methods to obtain chiral compounds has become an increasingly important and challenging research area in modern synthetic organic chemistry. In this account, we review recent work from our laboratory toward the synthesis of valuable chiral building blocks through transition-metal-catalyzed asymmetric hydrogenation and transfer hydrogenation of C=O, C=N and C=C bonds. Application to the synthesis of biologically relevant products is also described.

Novel chiral cobalt complexes containing a PNNP-type ligand were synthesized using a straightforward method. The structures of the cobalt complexes have been fully characterized by X-ray crystallography, high resolution mass spectrometry (HRMS), and electron paramagnetic resonance (EPR). Using H2 as the hydrogen source, the cobalt-catalyzed asymmetric hydrogenation of various ketones was investigated, and the corresponding chiral alcohols were afforded with up to 99 % yield and 95 % ee. To the best of our knowledge, this is the first example of a cobalt-catalyzed enantioselective hydrogenation of ketones with molecular hydrogen.

The reactivity difference between the hydrogenation of CO2 catalyzed by various ruthenium bidentate phosphine complexes was explored by DFT. In addition to the ligand dmpe (Me2 PCH2 CH2 PMe2 ), which was studied experimentally previously, a more bulky diphosphine ligand, dmpp (Me2 PCH2 CH2 CH2 PMe2 ), together with a more electron-withdrawing diphosphine ligand, PN(Me) P (Me2 PCH2 N(Me) CH2 PMe2 ), have been studied theoretically to analyze the steric and electronic effects on these catalyzed reactions. Results show that all of the most favorable pathways for the hydrogenation of CO2 catalyzed by bidentate phosphine ruthenium dihydride complexes undergo three major steps: cis-trans isomerization of ruthenium dihydride complex, CO2 insertion into the Ru-H bond, and H2 insertion into the ruthenium formate ion. Of these steps, CO2 insertion into the Ru-H bond has the lowest barrier compared with the other two steps in each preferred pathway. For the hydrogenation of CO2 catalyzed by ruthenium complexes of dmpe and dmpp, cis-trans isomerization of ruthenium dihydride complex has a similar barrier to that of H2 insertion into the ruthenium formate ion. However, in the reaction catalyzed by the PN(Me) PRu complex, cis-trans isomerization of the ruthenium dihydride complex has a lower barrier than H2 insertion into the ruthenium formate ion. These results suggest that the steric effect caused by the change of the outer sphere of the diphosphine ligand on the reaction is not clear, although the electronic effect is significant to cis-trans isomerization and H2 insertion. This finding refreshes understanding of the mechanism and provides necessary insights for ligand design in transition-metal-catalyzed CO2 transformation.

Catalytic asymmetric hydrogenation of ketones through the "metal-ligand cooperative mechanism" has been improved in terms of the efficiency, stereoselectivity, and scope of substrates by varying the arrangement of the catalyst structure and reaction conditions. Imino compounds are also smoothly converted to the optically active amines with appropriate catalysts. This type of catalyst exhibits excellent performance on the asymmetric isomerization of primary allylic alcohols into the optically active aldehydes. This personal account describes recent progress on these topics.

This is an overview of the hydride-containing catalysts prepared in the Morris group for the efficient hydrogenation of simple ketones, imines, nitriles and esters and the asymmetric hydrogenation and transfer hydrogenation of prochiral ketones and imines. The work was inspired by and makes use of Noyori metal-ligand bifunctional concepts involving the hydride-ruthenium amine-hydrogen HRuNH design. It describes the synthesis and some catalytic properties of hydridochloro, dihydride and amide complexes of ruthenium and in one case, osmium, with monodentate, bidentate and tetradentate phosphorus and nitrogen donor ligands. The iron hydride that has been identified in a very effective asymmetric transfer hydrogenation process is also mentioned. The link between the HMNH structure and the sense of enantioinduction is demonstrated by use of simple transition state models.

The asymmetric hydrogenation of quinolines in oligo(ethylene glycol)s (OEGs) and poly(ethylene glycol)s (PEGs) with chiral cationic ruthenium diamine complexes has been investigated. Interestingly, in liquid PEGs or long-chain OEGs, the Ru catalysts lost their reactivity. Upon the addition of a little MeOH, the hydrogenation of quinoline was switched "ON". Evidence from mass spectrometry and control experiments revealed that encapsulation of the quinolinium salt by PEG or long-chain OEG molecules through supramolecular interactions is possibly the main reason for such a switchable hydrogenation reaction. Moreover, the asymmetric hydrogenation of 2-substituted quinoline derivatives was achieved in triethylene glycol (3-OEG), thereby affording 1,2,3,4-tetrahydroquinolines with excellent reactivities and enantioselectivities (up to 99 % ee). Furthermore, the Ru catalyst could be readily recycled for both pure 3-OEG and biphasic 3-OEG/n-hexane systems without a clear loss of reactivity and enantioselectivity.

Herein we describe a new methodology for the asymmetric hydrogenation (AH) of 2-substituted pyridinium salts. An iridium catalyst based on a mixture of a chiral monodentate phosphoramidite and an achiral phosphine was shown to hydrogenate N-benzyl-2-arylpyiridinium bromides to the corresponding N-benzyl-2-arylpiperidines with full conversion and good enantioselectivity. The mechanism of the reaction under optimized conditions was investigated via kinetic measurements and isotopic labeling experiments. Our study suggests that the hydrogenation starts with a 1,4-hydride addition and that the enantiodiscriminating step involves the reduction of an iminium intermediate.

Iridium(I) complexes of phosphine-phosphite ligands efficiently catalyze the enantioselective hydrogenation of diverse seven-membered C=N-containing heterocyclic compounds (eleven examples; up to 97% ee). P-OP ligand L3, which incorporates an ortho-diphenyl substituted octahydrobinol phosphite fragment, provided the highest enantioselectivities in the hydrogenation of most of the heterocyclic compounds studied. The observed sense of stereoselection was rationalized by means of DFT calculations.

CF3 -substituted 1,3-diols were stereoselectively prepared in excellent enantiopurity and high yield from CF3 -substituted diketones by using an ansa-ruthenium(II)-catalyzed asymmetric transfer hydrogenation in formic acid/triethylamine. The intermediate mono-reduced alcohol was also obtained in very high enantiopurity by applying milder reaction conditions. In particular, CF3 C(O)-substituted benzofused cyclic ketones underwent either a single or a double dynamic kinetic resolution during their reduction.

Piano-stool ([(p-cymene)Ru(thz)Cl], 2) and six-coordinated ([Ru(thz)2(PPh3)2], 3) ruthenium complexes derived from 2-phenylthiazoline-4-carboxylic acid (Hthz, 1) were synthesized for the first time, and fully characterized using conventional methods. Also, the molecular structure of complex 3 was determined using X-ray analysis. These complexes were evaluated as catalysts for transfer hydrogenation of carbonyl compounds in the presence of isopropyl alcohol and KOtBu. Complex 2 was found to be more active than 3 in transfer hydrogenation. Copyright © 2016 John Wiley & Sons, Ltd.

A new type of planar chiral Shvo catalysts, where the chirality is based solely on different substitution flanking the CO function, was prepared and used for transfer hydrogenation of imines and ketones. The reduction of ketimines represented by N-(1-phenylethylidene)aniline and prochiral ketones such as phenyl trifluoromethyl ketone with 2-propanol was efficiently catalyzed by 0.5 mol% of the chiral Shvo catalyst to give high yields of the corresponding reduction products with the enantioselectivities in the range 45% to 64% ee.

The hydrogenation rates of C=C and C=O bonds in methyl vinyl ketone and crotonaldehyde were measured over a series of silica-supported Pt-Re catalysts (1:1 atomic ratio of Pt/Re) in liquid water with H2 (15 psig) at 333 K. The hydrogenation of methyl vinyl ketone did not produce any unsaturated alcohol because of the rapid hydrogenation of C=C relative to that of C=O. The addition of Re to Pt impacted the rate of C=C hydrogenation negatively in methyl vinyl ketone and crotonaldehyde, but promoted the selectivity of C=O hydrogenation in crotonaldehyde in which the unsaturated alcohol increased from 5 % on Pt to 21 % on Pt-Re. The addition of Re to Pt also promoted the rate of C=O hydrogenation in 2-butanone, whereas little effect was observed during the hydrogenation of butanal. The results of electron microscopy and H2 chemisorption on the Pt-Re catalysts showed the increasing interaction between Pt and Re with the increasing metal weight loading, and results from rate measurements suggest that oxophilic Re can be used to promote the Pt-catalyzed hydrogenation of carbonyl groups in multifunctional molecules.

Herein, we report the successful transformation of a 1(st) generation Grubbs metathesis catalyst into an asymmetric transfer hydrogenation (ATH) catalyst. Upon addition of a chiral amine ligand, an alcohol and a base, the 1(st) generation Hoveyda-Grubbs catalyst (HG-I) was found to promote the enantioselective reduction of acetophenone to 1-phenylethanol. After optimizing the order of addition and the reaction conditions, the substrate scope was assessed leading to enantiomeric excesses up to 97% ee. NMR experiments were run in order to get information about the in situ-generated ATH catalyst. Furthermore, the possibility to perform olefin metathesis and ketone transfer hydrogenation sequentially in one pot was demonstrated, and the first tandem olefin metathesis-ketone asymmetric transfer hydrogenation was carried out.

A ruthenocenyl phosphino-oxazoline-ruthenium complex (RuPHOX-Ru) was applied successfully to the asymmetric hydrogenation of β-secondary amino ketones, directly affording the corresponding chiral γ-secondary amino alcohols in up to 99% yield and with 99% ee. Reaction with β-(benzylamino)-1-phenylpropan-1-one could be performed on a gram-scale with a relatively low catalyst loading (up to 2000 S/C). The resulting hydrogenated product could be used for the synthesis of synthetically useful compounds.

The asymmetric transfer hydrogenation of alpha,beta-propargyl ketones catalyzed by an in situ formed ruthenium-hydroxyamide complex was explored. The acetylenic alcohols were isolated in good to excellent yields with excellent ee values (typically >90%) after short reaction times at room temperature.

An efficient protocol for the asymmetric reduction of sterically hindered ketones under transfer-hydrogenation conditions was developed. The corresponding chiral alcohols were obtained in good to excellent yields with enantiomeric excess values up to 99%. The role of the cation associated with the base present in the reduction reaction was investigated. In contrast to previous studies on this catalyst system, potassium ions rather than lithium ions significantly enhanced the reaction outcome.

A convenient and general asymmetric transfer hydrogenation of a wide array of 1-aryl-3,4-dihydroisoquinoline derivatives using a [RuIICl(η6-benzene)TsDPEN] complex in combination with a 5:2 HCOOH–Et3N azeotropic mixture as a hydrogen source was developed. Under mild reaction conditions, the described catalytic transformation secured a practical synthetic access to the corresponding valuable chiral 1-aryltetrahydroisoquinoline units with high atom economy, a broad substrate scope, high isolated yields (up to 97 %) and good to excellent enantioselectivities (up to 99 % ee). It was found that the stereochemical outcome of the reaction was strongly influenced by both the structure of the catalyst and the substituents present on the substrate. The synthetic utility of the present protocol has been demonstrated through the asymmetric synthesis of several biologically important alkaloids including the antiepileptic drug agent 1c, as well as (–)-nor-cryptostyline alkaloids I and II.

Selective catalytic reductions of nitriles are presented using the commercially available Ru-Macho-BH complex. A variety of aliphatic, aromatic and (hetero)cyclic nitriles including industrially important adipodinitrile are hydrogenated to the corresponding primary amines. Modelling suggests the reaction follows an outer sphere hydrogenation mechanism.