Hydrogenation Of Various Ketones Research Articles

Synthesis, characterization and theoretical studies of tris-cyclometalated rhodium(III) complexes: applications to asymmetric transfer hydrogenation of ketones

This paper presents the synthesis of {Rh[PyCH=C(O)Rn]3} complexes, where R1 = 4-cyanophenyl (L1), R2 = 3-nitrophenyl (L2), and R3 = 4-fluorophenyl (L3). These complexes were derived from the reactions of potassium hexachlororhodate(III) with related pyridinium ylides: PyCH=C(O)C6H4-p-CN (Y1), PyCH=C(O)C6H4-m-NO2 (Y2), and PyCH=C(O)C6H4-p-F (Y3). The reactions were carried out in methanol-water mixtures under mild conditions. The synthesized complexes were characterized using FT-IR, ESI-MS, multinuclear NMR (1H and 13C), and elemental analysis techniques (CHN). Furthermore, these Rh(III) compounds demonstrated excellent catalytic activity, high turnover number (TON), and turnover frequency (TOF) in the hydrogenation of various ketones, resulting in a series of alcohol products with outstanding yields and efficiencies. To investigate the structures of L1, L2, and L3, density function theory (DFT) calculations were performed at the BP86/def2-SVP level of theory. The study employed natural bond orbital analysis (NBO) and energy-decomposition analysis (EDA) to examine the strength and nature of the donor-acceptor bonds between the pyridinium ylide (Y) and Rh fragments in the complexes. Additionally, variations in natural orbitals for chemical valence (NOCV) were investigated.

Iridium Catalysts with f-Amphbinol Ligands: Highly Stereoselective Hydrogenation of a Variety of Ketones.

A series of novel and modular ferrorence-based amino-phosphine-binol (f-amphbinol) ligands have been successfully synthesized. The f-amphbinol ligands exhibited extremely high air stability and catalytic efficiency in the Ir-catalyzed stereoselective hydrogenation of various ketones to afford corresponding stereodefined alcohols with excellent results (full conversions, cis/trans >99:1, and 83% → 99% ee, TON up to 500 000). Control experiments have shown that -OH and -NH groups played a key role in this stereoselective hydrogenation.

Preparation of catechol boronate esters enabled by N → B dative bond as efficient, stable, and green catalysts for the transfer hydrogenation of various ketones

A series of new structurally related catechol boronate esters enabled by N → B dative bond of general composition (B1-B4) and (B1N-B4N) were designed and synthesized for the transfer hydrogenation of various ketones, as catalysts. The structures of the synthesized trigonal-planar and tetrahedral catechol boronate esters forming dative bonds with neutral base were well-elucidated by NMR (1H, 13C, and 11B), FT-IR, UV–Vis, fluorescence, and LC-MS/MS spectroscopy, melting point and microanalysis. With the development of a more active and stable catalytic system for transfer hydrogenation of ketones in mind, all catechol boronate esters were tested as catalysts for the transfer hydrogenation of aromatic ketones, showing good activity in this reaction. Particularly, it was proved that the mononuclear molecules can afford an efficient catalytic conversion compared to the corresponding dinuclear boronate esters in transfer hydrogenation catalytic studies. Among the catalysts, (B4) and (B4N) are the most active catalysts and catalytic activity of (B4) was generally much higher in the studied hydrogen transfer reactions than that of (B4N) under mild conditions in isoPrOH. This clearly suggests that catechol boronate esters are also one of the propitious catalyst candidates and are worthy of further investigations.

Efficient transfer hydrogenation of ketones using molybdenum complexes by comprehensively verifying the auxiliary ligands.

Molybdenum complexes ligated with N1,N1-dialkyl-N2-(5,6,7,8-tetrahydroquinolin-8-yl)ethane-1,2-diamines and auxiliary ligands, providing various structural features, were developed: [NNH/NNHN]Mo(CO)4/3 (Mo1-Mo3), [NNHN]Mo(CO)2Br (Mo4-Mo5), [NNH]Mo(CO)(η3-C3H5)Br (Mo6) and [NNHN/S]Mo(CO)(PPh3)2 (Mo7-Mo8). All the complexes were highly active in the transfer hydrogenation (TH) of a model substrate (acetophenone), providing excellent yields of 1-phenylethanol. The structural variation in the ligand framework had a modest effect on the catalyst performance as compared to the changes in the auxiliary ligands Br, PPh3 and CO. This structural evolution provided the complex [Mo(NNH)(η3-C3H5)(CO)2Br] (Mo6) as the most effective catalyst not only for the transfer hydrogenation of acetophenone but also for a wide range of diverse ketones (up to 43 examples). Moreover, easy purification of the products by only removing the acetone byproduct is another noteworthy feature of this environmentally friendly route.

Chiral salen - Ni (II) based spherical porous silica as platform for asymmetric transfer hydrogenation reaction and synthesis of potent drug intermediate montekulast

Heterogeneous catalyst has an edge over homogeneous systems in terms of recyclability, activity, stability and recovery. Silica has evolved as a good support material in heterogeneous systems due to its stability and ability to get modified as per the end application. Herein, we report a novel chiral Ni-Schiff base derived catalyst and its immobilization into mesoporous silica which was synthesized by post-grafting process. The chiral catalyst demonstrated remarkably high catalytic activity, enantioselectivity (up to 99 % enantiomers excess) for heterogeneous asymmetric transfer hydrogenation of various ketones. The developed catalyst was characterized by Ultraviolet-visible spectroscopy (UV–vis), Fourier-Transform Infrared spectroscopy (FT-IR), X-ray Powder Diffraction (XRD), Brunauer-Emmett-Teller (BET isotherm), Scanning Electron Microscopy – Energy Dispersive X-ray Spectroscopy (SEM-EDX), High Resolution – Transmission Electron Microscopy (HR-TEM), Vibrating Sample Magnetometer (VSM), X-ray Photoelectron Spectroscopy (XPS) and elemental analysis. The catalyst could be recovered and reused for multiple consecutive runs without losing the enantioselectivity. The chiral catalyst was used in asymmetric transfer hydrogenation reaction for synthesizing enantiomerically pure drug intermediate Montekulast.

Synthesis of cis‐1,2‐diol‐type chiral ligands and their dioxaborinane derivatives: Application for the asymmetric transfer hydrogenation of various ketones and biological evaluation

Two cis‐1,2‐diol‐type chiral ligands (T1 and T2) and their tri‐coordinated chiral dioxaborinane (T(1–2)B(1–2)) and four‐coordinated chiral dioxaborinane adducts with 4‐tert‐butyl pyridine sustained by N → B dative bonds (T(1–2)B(1–2)‐N) were synthesized and characterized by various spectroscopic techniques such as NMR (1H, 13C, and 11B), FT‐IR and UV–Vis spectroscopy, LC–MS/MS, and elemental analysis. It was suggested that both ferrocene and trifluoromethyl groups played key roles in the catalytic and biological studies because they could tune the solubility of the chiral dioxaborinane complexes and adjust the strength of intermolecular interactions. To assess the biological activities of newly synthesized chiral dioxaborinane compounds, DPPH (2,2‐diphenyl‐1‐picrylhydrazyl) radical scavenging, reducing power, antibacterial, DNA binding, and DNA cleavage activities were tested. Then, all chiral dioxaborinane complexes were investigated as catalysts for the asymmetric transfer hydrogenation of various ketones under suitable conditions. The results indicated that the chiral dioxaborinane catalysts performed well with high yields.

Reduced graphene oxide/iron oxide hybrid composite material as an efficient magnetically separable heterogeneous catalyst for transfer hydrogenation of ketones

Reduced graphene oxide was synthesized and functionalized with FeSO4⋅7H2O to form a reduced graphene oxide/iron oxide hybrid composite. The hybrid composite was extensively characterized using various techniques. Its application for transfer hydrogenation of various ketones was studied. The investigation showed that it serves as a good catalyst for transfer hydrogenation of aromatic and some aliphatic ketones resulting in excellent isolated yields (97–99%) of products. It is magnetically separable showing good reusability. The products were characterized and compared with authentic ones.

Catalysts for the asymmetric transfer hydrogenation of various ketones from [3-[(2S)-2-[(diphenylphosphanyl)oxy]-3-phenoxypropyl]-1-methyl-1H-imidazol-3-ium chloride] and [Ru(η6-arene)(μ-Cl)Cl]2, Ir(η5-C5Me5)(μ-Cl)Cl]2 or [Rh(μ-Cl)(cod)

The combination of [3-[(2S)-2-[(diphenylphosphanyl)oxy]-3-phenoxypropyl]-1-methyl-1H-imidazol-3-ium chloride] with [Ru(η6-arene)(μ-Cl)Cl]2, Ir(η5-C5Me5)(μ-Cl)Cl]2 or [Rh(μ-Cl)(cod)]2, in the presence of KOH/isoPrOH, has been found to generate catalysts that are capable of enantioselectively reducing alkyl, aryl ketones to the corresponding (R)-alcohols. Under optimized conditions, when the catalysts were applied to the asymmetric transfer hydrogenation, we obtained the secondary alcohol products in high conversions and enantioselectivities using only 0.5 mol% catalyst loading. In addition, [3-[(2S)-2-{[(chloro(ɳ4-1,5-cyclooctadiene)rhodium)diphenyl phosphanyl] oxy}-3-phenoxypropyl]-1-methyl-1H-imidazol-3-ium chloride], (6) complex is much more active than the other analogous complexes in the transfer hydrogenation. Catalyst 6 acts as excellent catalysts, giving the corresponding (R)-1-phenyl ethanol in 99% conversion in 30 min (TOF ≤ 396 h−1) and in high enantioselectivity (92% ee).

Lutidine-Based Chiral Pincer Manganese Catalysts for Enantioselective Hydrogenation of Ketones.

A series of MnI complexes containing lutidine-based chiral pincer ligands with modular and tunable structures has been developed. The complex shows unprecedentedly high activities (up to 9800 TON; TON=turnover number), broad substrate scope (81 examples), good functional-group tolerance, and excellent enantioselectivities (85-98 % ee) in the hydrogenation of various ketones. These aspects are rare in earth-abundant metal catalyzed hydrogenations. The utility of the protocol have been demonstrated in the asymmetric synthesis of a variety of key intermediates for chiral drugs. Preliminary mechanistic investigations indicate that an outer-sphere mode of substrate-catalyst interactions probably dominates the catalysis.

Lutidine‐Based Chiral Pincer Manganese Catalysts for Enantioselective Hydrogenation of Ketones

AbstractA series of MnI complexes containing lutidine‐based chiral pincer ligands with modular and tunable structures has been developed. The complex shows unprecedentedly high activities (up to 9800 TON; TON=turnover number), broad substrate scope (81 examples), good functional‐group tolerance, and excellent enantioselectivities (85–98 % ee) in the hydrogenation of various ketones. These aspects are rare in earth‐abundant metal catalyzed hydrogenations. The utility of the protocol have been demonstrated in the asymmetric synthesis of a variety of key intermediates for chiral drugs. Preliminary mechanistic investigations indicate that an outer‐sphere mode of substrate–catalyst interactions probably dominates the catalysis.

Half‒Sandwich (η6‒p‒Cymene) Ruthenium(II) complexes bearing 5‒Amino‒1‒Methyl‒3‒Phenylpyrazole Schiff base ligands: Synthesis, structure and catalytic transfer hydrogenation of ketones

New (η6‒p‒cymene) ruthenium(II) complexes containing Schiff base ligands of the general composition [RuCl(η6‒p‒cymene)(L1‒3)] have been synthesized. The complexes were characterized by analytical and spectral (FT‒IR, UV–Vis, 1H NMR and 13C NMR) methods. The molecular structure of the representative complex [RuCl(η6‒p‒cymene)(L3)] 6 was determined by single crystal X−ray diffraction studies, revealing a pseudo-octahedral piano stool geometry around ruthenium(II) ion. Further, one of the complexes 6 was screened for their efficiency as a catalyst in the transfer hydrogenation of various ketones to alcohols in the presence of KOH and 2‒propanol showed an excellent conversion up to 99%. Under the optimized conditions, the influence of base, reaction temperature and substrate scope was also reported.

Pyridyl based ruthenium(II) catalyst precursors and their dihydride analogues as the catalytically active species for the transfer hydrogenation of ketones

In this study we describe the one-pot and high yield synthesis of the ruthenium(II) complex cis-dichloride [RuCl2(PPh3)2(L1)] (L1 = 4-methyl-2-(2′-pyridyl)quinoline) (1). The solid state structure of L1 is described. The catalytic activity of 1 in the transfer hydrogenation of various ketones by 2-propanol at 82 °C, has been studied and compared with the activity of the known catalyst precursors cis-[RuCl2(PPh3)2(L2)] (L2 = 2-(2'-pyridyl)quinoline) (2), cis-[RuCl2(PPh3)2(L3)] (L3 = 2-(2′-pyridyl)quinoxaline) (3) and cis-[RuCl2(PPh3)2(bipy)] (bipy = 2,2′-bipyridine) (4). The ruthenium monohydride complex [RuHCl(PPh3)2(L3)] 3-H (Cl cis to H) was prepared from the reaction of 3 with 2.5 equivalents of a KOiPr solution. Reaction of 3 with 10 equivalents of KOiPr yields the cis-[RuH2(PPh3)2(L3)] (3-H2). Treatment of 1, 2 and 4 with KOiPr (in excess) affords the ruthenium cis-dihydride complexes [RuH2(PPh3)2(L1)] (1-H2), [RuH2(PPh3)2(L2)] (2-H2) and [RuH2(PPh3)2(bipy)] (4-H2). The formation of 1-H2, 2-H2, 3-H2 and 4-H2 is supported by NMR spectroscopic data. The cis-dihydrides 1-H2 to 4-H2 catalyze successfully the transfer hydrogenation of benzophenone to benzhydrol in the absence of a base, suggesting that presumably the active catalyst is a ruthenium dihydride complex (RuH2). Catalyst 1 has been potentially recovered and reused at least four times.

A new class of well-defined ruthenium catalysts for enantioselective transfer hydrogenation of various ketones

A pair of novel optically pure phosphinite ligands were synthesized by ring opening reaction of chiral amines with (R)-styrene oxide or (S)-glycidyl phenyl ether oxide using a straightforward method in high yields and their ruthenium complexes were described in detail. The ruthenium complexes proved to be highly efficient catalysts for the enantioselective hydrogenation of ketones, affording products up to 99% ee. The results showed that the corresponding chiral alcohols could be obtained with high activity and excellent enantioselectivities at the desired temperature. (2S)-1-{benzyl[(1S)-1-(naphthalen-1-yl)ethyl]amino}-3-phenoxypropan-2-yl diphenylphosphinito[dichloro(η6-benzene)ruthenium (II)] acts an excellent catalyst in the reduction of ketones, giving the corresponding alcohol up to 99% ee.

Catechol-type ligand containing new modular design dioxaborinane compounds: Use in the transfer hydrogenation of various ketones

A novel class of tricoordinate dioxaborinane compounds, which have the general formula [B1(L1–5)] and [B2(L1–5)], were designed and synthesized by the corresponding catechol-type ligands (L1–L5) at ambient temperature. All the new compounds were fully characterized by NMR (1H, 13C, and 11B), FT-IR, UV–vis, LC-MS spectroscopy, and melting point analysis and microanalysis. The dioxaborinane [B1(L1–5)] and [B2(L1–5)] compounds were investigated as catalyst for the transfer hydrogenation of various ketones under suitable conditions. Particularly, it was proved that the ferrocene-based dioxaborinane [B1(L1–5)] molecules can afford an efficient catalytic conversion compared to corresponding 3,5-bis(trifluoromethyl)phenyl-based [B2(L1–5)] dioxaborinanes in transfer hydrogenation catalytic studies.

Distinct Promotive Effects of 1,8‐Diazabicyclo[5.4.0]undec‐7‐ene (DBU) on Polymer Supports in Copper‐Catalyzed Hydrogenation of C=O Bonds

AbstractAn amidine base‐containing polymer, polystyrene‐bound 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (PS‐DBU), proved to serve as a prominent catalyst support. The combined use of selected copper salts with PS‐DBU in the catalytic hydrogenation of acetophenone qualifies DBU as beneficial to generate catalytically active species and stabilize them on the polymer. Catalyst preparation and characterization reveal that the active copper species is in a low‐valent state and the nanosized particles possibly grow on the amidine structure. The high immobilization ability of PS‐DBU almost entirely prohibited copper leaching to the product over six cycles of hydrogenation and catalyst recovery. The copper catalyst attached to PS‐DBU specifically promotes the hydrogenation of various ketones and aldehydes under 10 atm of H2 at 90 °C to afford alcoholic products in satisfactory yields.

Ru(II) mediated C[sbnd]H activation of 1-(biphenylazo)naphthol: Synthesis and catalytic evaluation for transfer hydrogenation of ketones

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.

New Rh(III) complexes of 5‐methyl‐5‐(pyridyl)‐2,4‐imidazolidenedione: Synthesis, X‐ray structure, electrochemical study and catalytic behaviour for hydrogenation of ketones

We describe the reaction of anion [RhCl6]3− with a series of hydantoin ligands (HL1, HL2 and HL3 = 5‐methyl‐5‐(2‐, 3‐ and 4‐pyridyl)‐2,4‐imidazolidenedione, respectively). Based on spectroscopic, cyclic voltammetric, elemental and MS analyses, the complexes have the general formula K[RhCl2(L1)2] (1), cis‐ and trans‐K[RhCl4(HL2)2] (2a and 2b) and cis‐ and trans‐K[RhCl4(HL3)2] (3a and 3b). Complexes 2a, 2b, 3a and 3b were characterized successfully using infrared, 1H NMR and 13C NMR spectral analyses. Dissolution of complex 1 in dimethylsulfoxide (DMSO) led to elimination of one KL1 ligand and coordination of two DMSO molecules as ligands and transformation of this complex to cis‐ and trans‐[RhCl2L1(DMSO)2] (1a and 1b). Recrystallization led to separation and isolation of crystals of 1a from the initial mixture. X‐ray analysis results showed that this complex was crystallized as solvated complex cis‐[RhCl2L1(DMSO)2]DMSO. The catalytic activity of these complexes was then evaluated for the hydrogenation of various ketones.

Comparative transfer hydrogenation performance of homogeneous and heterogeneous ruthenium (II) catalysts derived from a Schiff base ligand

A new Schiff base ligand (E)-4-(((pyridin-2-ylmethylene)amino)methyl)phenol (L1H) 1 was synthesized and grafted to solid support successfully. Mononuclear Ru(II) complex 2, its solid supported analogue 4 and heterogeneous complex 5 were synthesized with [RuCl2(p-cymene)]2 and RuCl2(PPh3)dppb.According to the UV–visible, IR and NMR data, the Ru (II) complexes are formed by the coordination of both nitrogen atoms of the ligand. Molecular structures of the L1H 1 was determined by single crystal X-ray diffraction study. The Ruthenium (II) complexes 2, 4 and 5 were used as catalysts for the transfer hydrogenation of various ketones in 2-propanol. Following the comparison of complexes 2, 4 and 5 between each other, it was observed that immobilized complexes have higher catalytic activity against the homogeneous structure. The results showed that the diphosphine incorporated complex 5 is more efficient than the other Ru (II) complexes.

ChemInform Abstract: Synthesis and Catalytic Evaluation of Ruthenium(II) Benzhydrazone Complex in Transfer Hydrogenation of Ketones.

AbstractThe new Ru‐catalyst shows excellent activity in the transfer hydrogenation of various ketones.

Enantioselective Hydrogenation of Ketones Catalyzed by Chiral Cobalt Complexes Containing PNNP Ligand

AbstractNovel 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.