- Isomer and enantiomer separation of 2- and 4-alkyl-cyclohexanols by stereoselective complex formation with O,O′-dibenzoyl-(2R,3R)-tartaric acid
-
Stereoisomeric mixtures of 2- and 4-alkyl-cyclohexanols form complex with O,O′-dibenzoyl-(2R,3R)-tartaric acid. The diastereoisomer complex formation can be used for isomer and enatiomer separation as it is trans- and enantioselective in the case of 2-alkyl-cyclohexanols and trans-selective in the case of 4-alkyl-cyclohexanols.
- Kassai,Balint,Juvancz,Fogassy,Kozma
-
-
Read Online
- Structural, kinetic, and DFT studies of the transfer hydrogenation of ketones mediated by (pyrazole)pyridine iron(II) and nickel(II) complexes
-
A series of iron(ii) and nickel(ii) complexes chelated by 2-pyrazolyl(methyl)pyridine (L1), 2,6-bis(pyrazolylmethyl)pyridine (L2), and 2,6-bis(pyrazolyl)pyridine (L3) ligands have been investigated as transfer hydrogenation (TH) catalysts for a range of ketones. Nine chelates in total were studied: [Ni(L1)Br2] (1), [Ni(L1)Cl2] (2), [Fe(L1)Br2] (3), [Ni(L2)Br2] (4), [Ni(L2)Br2] (5), [Fe(L2)Cl2] (6), [Ni(L3)Br2] (7), [Ni(L3)Br2] (8), and [Fe(L3)Cl2] (9). Attempted crystallization of complexes 4 and 6 afforded stable six-coordinate cationic species 4a and 6a with a 2:1 ligand:metal (L:M) stoichiometry, as opposed to the monochelates that function as precursors to catalytic species for TH reactions. Crystallization of 7·4H2O and 8·2H2O, in contrast, afforded tri- and bis(aqua) salts of L3 chelated to Ni(ii) in a 1:1 L:M stoichiometry, respectively. Complexes 1-9 formed active catalysts for the TH of a range of ketones in 2-propanol at 82 °C. Both the nature of the metal ion and ligand moiety had a discernible impact on the catalytic activities of the complexes, with nickel(ii) chelate 5 affording the most active catalyst (kobs, 4.3 × 10-5 s-1) when the inductive phase lag was appropriately modelled in the kinetics. Iron(ii) complex 3 formed the most active TH catalyst without a significant inductive phase lag in the kinetics. DFT and solid angle calculations were used to rationalize the kinetic data: both steric shielding of the metal ion and electronic effects correlating with the metal-ligand distances appear to be significant factors underpinning the reactivity of 1-9. Catalysts derived from 1 and 9 exhibit a distinct preference for aryl ketone substrates, suggesting the possible involvement of π-type catalyst?substrate adducts in their catalytic cycles. A catalytic cycle involving only 4 steps (after induction) with stable DFT-simulated structures is proposed which accounts for the experimental data for the system.
- Magubane, Makhosazane N.,Nyamato, George S.,Ojwach, Stephen O.,Munro, Orde Q.
-
-
Read Online
- Selective Reductions. 38. Reaction of Thexylchloroborane-Methyl Sulfide Complex in Methylene Chloride with Selected Organic Compounds Containing Representative Functional Groups. Comparison of the Reducing Characteristics of Thexylchloroborane, Thexylborane, and Diborane
-
The approximate rate and stoichiometry of the reaction of excess thexylchloroborane-methyl sulfide complex, ThxBHCL*SMe2, with 56 selected organic compounds containing representative functional groups under standard conditions (methylene chloride, 0 deg C) were determined order to define the characteristics of the reagent for selective reductions.The selectivity of the reagent was also compared to the selectivities of thexylborane and diborane.Alcohols and phenol react with the reagent at a fast rate to evolve an equivalent of hydrogen without any further reduction .Amines and aliphatic thiols do not form any hydrogen, while benzenethiol shows partial hydrogen formation.Aldehydes and ketones are reduced rapidly and quantitatively to give the corresponding alcohols.Unlike thexylborane and diborane, the reagent shows good stereoselectivity toward cyclic ketones.For example, 2-methylcyclohexanone is reduced to the less stable isomer, cis-2-methylcyclohexanol, in a high ratio (99.9percent cis isomer at -78 deg C).Cinnamaldehyde is reduced rapidly to cinnamyl alcohol, and any further reduction of the double bond is very slow under these conditions. p-Benzoquinone reacts only partially with the reagent while anthraquinone is totally unreactive.Carboxylic acids liberate 1 equiv of hydrogen rapidly and are further reduced to the corresponding aldehydes in good yields and purity.Acid chlorides react sluggishly with the reagent to use 2 equiv of hydride, while acetic anhydride utilizes 3 equiv of hydride to yield acetaldehyde and ethanol.On the other hand, cyclic anhydrides, such as succinic anhydride and phthalic anhydride, react very slowly with the reagent.Esters are almost inert toward thexylchloroborane. γ-Butyrolactone and phthalide are only partially reduced under the reaction conditions.Isopropenyl acetate utilizes 3 equiv og hydride to yield the corresponding acetaldehyde and presumably the hydroboration product of propylene.Only a partial reduction of epoxides can be observed.Primary amides like caproamide and benzamide evolve 1 equiv of hydrogen, but further reaction is very slow.Tertiary amides are almost inert under these conditions.Capronitrile reacts with the reagent to use 2 equiv of hydride in less than 24 h, while the reaction between benzonitrile and thexylchloroborane is sluggish.Nitrobenzene and 1-nitropropane do not react with the reagent, while azobenzene reacts only partially.Azoxybenzene consumes 2 equiv of hydride in 48 h.Only a sluggish reaction between thexylchloroborane and cyclohexanone oxime or phenyl isocyanate can be observed.Pyridine does not react, while pyridine N-oxide utilizes 3 equiv of hydride.Of the sulfur compounds tested, only dimethyl sulfoxide is reduced by the reagent to form the corresponding sulfide, while other sulfur compounds, such as disulfide, sulfide, and sulfone, are inert under these conditions.Altough sulfonic acids evolve hydrogen, no further reduction is observed.
- Brown, Herbert C.,Nazer, Behrooz,Cha, Jim Soon,Sikorski, James A.
-
-
Read Online
- Hydrogen-atom and oxygen-atom transfer reactivities of iron(
-
A series of iron(ii) complexes with the general formula [FeII(L2-Qn)(L)]n+ (n = 1, L = F?, Cl?; n = 2, L = NCMe, H2O) have been isolated and characterized. The X-ray crystallographic data reveals that
- Banerjee, Sridhar,Haukka, Matti,Hossain, Md. Kamal,Huelsmann, Ricardo Dagnoni,Martendal, Edmar,Munshi, Sandip,Nordlander, Ebbe,Paine, Tapan K.,Peralta, Rosely,Singh, Reena,Sinha, Arup,Valiati, Andrei Felipe,Wendt, Ola F.,Xavier, Fernando,Yiga, Solomon
-
supporting information
p. 870 - 884
(2022/02/01)
-
- Chemoselective and Tandem Reduction of Arenes Using a Metal–Organic Framework-Supported Single-Site Cobalt Catalyst
-
The development of heterogeneous, chemoselective, and tandem catalytic systems using abundant metals is vital for the sustainable synthesis of fine and commodity chemicals. We report a robust and recyclable single-site cobalt-hydride catalyst based on a porous aluminum metal–organic framework (DUT-5 MOF) for chemoselective hydrogenation of arenes. The DUT-5 node-supported cobalt(II) hydride (DUT-5-CoH) is a versatile solid catalyst for chemoselective hydrogenation of a range of nonpolar and polar arenes, including heteroarenes such as pyridines, quinolines, isoquinolines, indoles, and furans to afford cycloalkanes and saturated heterocycles in excellent yields. DUT-5-CoH exhibited excellent functional group tolerance and could be reusable at least five times without decreased activity. The same MOF-Co catalyst was also efficient for tandem hydrogenation–hydrodeoxygenation of aryl carbonyl compounds, including biomass-derived platform molecules such as furfural and hydroxymethylfurfural to cycloalkanes. In the case of hydrogenation of cumene, our spectroscopic, kinetic, and density functional theory (DFT) studies suggest the insertion of a trisubstituted alkene intermediate into the Co–H bond occurring in the turnover limiting step. Our work highlights the potential of MOF-supported single-site base–metal catalysts for sustainable and environment-friendly industrial production of chemicals and biofuels.
- Antil, Neha,Kumar, Ajay,Akhtar, Naved,Begum, Wahida,Chauhan, Manav,Newar, Rajashree,Rawat, Manhar Singh,Manna, Kuntal
-
supporting information
p. 1031 - 1040
(2022/01/19)
-
- Synthesis and structural elucidation of (pyridyl)imine Fe(II) complexes and their applications as catalysts in transfer hydrogenation of ketones
-
Reactions of (pyridyl)imine ligands: 2,6-diisopropyl-N-[(pyridine-2-yl)methylene]aniline (L1), 2,6-diisopropyl-N-[(pyridine-2-yl)ethylidene]aniline (L2), 2,6-dimethyl-N-[(pyridine-2-yl)methylene]aniline (L3), 2,6-dimethyl-N-[(pyridine-2-yl)ethylidene]aniline (L4) and N-[(pyridine-2-yl)methylene]aniline (L5) with FeCl2 salt afforded the corresponding paramagnetic Fe(II) complexes [Fe(L1)2Cl][FeCl4] (Fe1), [Fe(L2)2Cl][FeCl4] (Fe2), [Fe(L3)2Cl][FeCl4] (Fe3), [Fe(L4)2Cl][FeCl4], (Fe4), [Fe(L5)2Cl2] (Fe5) in good yields. On the other hand, reactions of L1 with FeCl2 in the presence of NaPF6 afforded complex [Fe(L1)2Cl][PF6] (Fe6) in moderate yields. Molecular structures of complexes Fe1 and Fe2 reveal the formation of cationic species containing two N^N bidentate ligands and one chlorido co-ligand to give five-coordinate geometry with [FeCl4]? as counter-anion. On the other hand, complex Fe5, is an octahedral neutral species containing two bidentate L5 and two chlorido ligands. All the complexes (Fe1–Fe6) formed active catalysts in the transfer hydrogenation of ketones affording average yields of about 85%. The ligand architecture, reaction conditions and nature of substrate influenced the catalytic activities of the complexes. Mercury and subs-stoichiometric poisoning tests pointed to the existence of both Fe(0) nanoparticles and homogeneous Fe(II) species as the active intermediates.
- Tsaulwayo, Nokwanda,Kumah, Robert T.,Ojwach, Stephen O.
-
-
- Applications of imino-pyridine Ni(II) complexes as catalysts in the transfer hydrogenation of ketones
-
Five imino-pyridine Ni(II) complexes: [{Ni(L1)Cl2}2] Ni1; [{Ni(L2)Cl2}2] Ni2; [{Ni(L3)Cl2}2] Ni3; [{Ni(L4)Cl2}2] Ni4 and [Ni(L5)2Cl2] Ni5 derived from ligands 2,6-diisopropyl-N-[(pyridin-2-yl) methylene] aniline (L1); 2,6-diisopropyl-N-[(pyridin-2-yl) ethylidene]aniline (L2); 2,6-dimethyl-N-[(pyridin-2-yl) methylene] aniline (L3); 2,6-dimethyl-N-[(pyridin-2-yl) ethylidene] aniline (L4) and N-[(pyridin-2-yl) methylene] aniline (L5) were evaluated as catalysts in the transfer hydrogenation of ketones. The Ni(II) complexes demonstrated moderate catalytic activities giving a turnover number (TON) of up to 126 at catalyst loading of 0.5 mol%. The structure of the complexes and nature of ketone substrate influenced the catalytic activities of the complexes. Deactivation studies using mercury and sub-stoichiometric poisoning experiments pointed to the presence of both Ni(0) nanoparticles and Ni(II) homogeneous as the active species.
- Tsaulwayo, Nokwanda,Kumah, Robert.T.,Ojwach, Stephen.O.
-
-
- Application of robust ketoreductase from Hansenula polymorpha for the reduction of carbonyl compounds
-
Enzyme-catalysed asymmetric reduction of ketones is an attractive tool for the production of chiral building blocks or precursors for the synthesis of bioactive compounds. Expression of robust ketoreductase (KRED) from Hansenula polymorpha was upscaled and applied for the asymmetric reduction of 31 prochiral carbonyl compounds (aliphatic and aromatic ketones, diketones and β-keto esters) to the corresponding optically pure hydroxy compounds. Biotransformations were performed with the purified recombinant KRED together with NADP+ recycling glucose dehydrogenase (GDH, Bacillus megaterium), both overexpressed in Escherichia coli BL21(DE3). Maximum activity of KRED for biotransformation of ethyl-2-methylacetoacetate achieved by the high cell density cultivation was 2499.7 ± 234 U g–1DCW and 8.47 ± 0.40 U·mg–1E, respectively. The KRED from Hansenula polymorpha is a very versatile enzyme with broad substrate specificity and high activity towards carbonyl substrates with various structural features. Among the 36 carbonyl substrates screened in this study, the KRED showed activity with 31, with high enantioselectivity in most cases. With several ketones, the Hansenula polymorpha KRED catalysed preferentially the formation of the (R)-secondary alcohols, which is highly valued.
- Petrovi?ová, Tatiana,Gyuranová, Dominika,Pl?, Michal,Myrtollari, Kamela,Smonou, Ioulia,Rebro?, Martin
-
-
- Discovery of New Carbonyl Reductases Using Functional Metagenomics and Applications in Biocatalysis
-
Enzyme discovery for use in the manufacture of chemicals, requiring high stereoselectivities, continues to be an important avenue of research. Here, a sequence directed metagenomics approach is described to identify short chain carbonyl reductases. PCR from a metagenomic template generated 37 enzymes, with an average 25% sequence identity, twelve of which showed interesting activities in initial screens. Six of the most productive enzymes were then tested against a panel of 21 substrates, including bulkier substrates that have been noted as challenging in biocatalytic reductions. Two enzymes were selected for further studies with the Wieland Miescher ketone. Notably, enzyme SDR-17, when co-expressed with a co-factor recycling system produced the anti-(4aR,5S) isomer in excellent isolated yields of 89% and 99% e.e. These results demonstrate the viability of a sequence directed metagenomics approach for the identification of multiple homologous sequences with low similarity, that can yield highly stereoselective enzymes with applicability in industrial biocatalysis. (Figure presented.).
- Newgas, Sophie A.,Jeffries, Jack W. E.,Moody, Thomas S.,Ward, John M.,Hailes, Helen C.
-
p. 3044 - 3052
(2021/04/26)
-
- Reduced Amino Acid Schiff Base-Iron(III) Complexes Catalyzing Oxidation of Cyclohexane with Hydrogen Peroxide
-
The reduced amino acid Schiff base ligands have been prepared and were coordinated with ferric chloride to generate the iron(III) complexes. The ligands and complexes have been characterized using FT-IR, UV-vis, elemental analysis, ICP-AES analysis, mass spectra etc. After the structural characterization, these complexes were applied for the oxidation of cyclohexane using hydrogen peroxide as the oxidant under mild conditions. The activity tests showed that the L-phenylalanine-derived reduced Schiff base iron(III) complex(Ph?FeCl) afforded the highest yield of cyclohexanol and cyclohexanone(total yield up to 23.2 %). Notably, the Ph?FeCl complex catalyzes the reaction via a heterogeneous approach, allowing the complex to be separated and recycled conveniently after the oxidation reaction. Besides, the Ph?FeCl catalyst can also be extended for the selective oxidation of other alkanes and aromatics into alcohols, ketones and phenols etc. Finally, the reaction mechanism of cyclohexane oxidation on the iron(III) complex was proposed as well by the free radical inhibitors and EPR study of active intermediates.
- Zheng, Anna,Zhou, Qingqing,Ding, Bingjie,Li, Difan,Zhang, Tong,Hou, Zhenshan
-
p. 3385 - 3395
(2021/08/23)
-
- Catalytic role of metals supported on SBA-16 in hydrodeoxygenation of chemical compounds derived from biomass processing
-
Hydrodeoxygenation (HDO) carried out at high temperatures and high hydrogen pressures is one of the alternative methods of upgrading pyrolytic oils from biomass, leading to high quality biofuels. To save energy, it is important to carry out catalytic proc
- Szczyglewska, Paulina,Feliczak-Guzik, Agnieszka,Jaroniec, Mietek,Nowak, Izabela
-
p. 9505 - 9517
(2021/03/16)
-
- Aliphatic C–H hydroxylation activity and durability of a nickel complex catalyst according to the molecular structure of the bis(oxazoline) ligands
-
Applicability of the oxazoline-based compounds, bis(2-oxazolynyl)methane (BOX) and 2,6-bis(2-oxazolynyl)pyridine (PyBOX), as supporting ligands of nickel(II) complexes for the catalysis of aliphatic C–H hydroxylation with m-CPBA (meta-chloroperoxybenzoic acid) was explored. Substituent groups at the fourth and fifth positions of oxazoline rings and the bridgehead carbon atom of the BOX derivatives affected the catalytic performances toward cyclohexane hydroxylation. Presence of dioxygen led to a reduced catalytic performance of the nickel complexes, except in the case of a fully substituted BOX ligand complex.
- Hikichi, Shiro,Izumi, Takashi,Matsuba, Naki,Nakazawa, Jun
-
-
- Efficient alkane hydroxylation catalysis of nickel(ii) complexes with oxazoline donor containing tripodal tetradentate ligands
-
Tris(oxazolynylmethyl)amine TOAR(where R denotes the substituent groups on the fourth position of the oxazoline rings) complexes of nickel(ii) have been synthesized as catalyst precursors for alkane oxidation withmeta-chloroperoxybenzoic acid (m-CPBA). The molecular structures of acetato, nitrato,meta-chlorobenzoato and chlorido complexes with TOAMe2have been determined using X-ray crystallography. The bulkiness of the substituent groups R affects the coordination environment of the nickel(ii) centers, as has been demonstrated by comparison of the molecular structures of chlorido complexes with TOAMe2and TOAtBu. The nickel(ii)-acetato complex with TOAMe2is an efficient catalyst precursor compared with the tris(pyridylmethyl)amine (TPA) analogue. Oxazolynyl donors’ strong s-electron donating ability will enhance the catalytic activity. Catalytic reaction rates and substrate oxidizing position selectivity are controlled by the structural properties of the R of TOAR. Reaction of the acetato complex with TOAMe2andm-CPBA yields the corresponding acylperoxido species, which can be detected using spectroscopy. Kinetic studies of the decay process of the acylperoxido species suggest that the acylperoxido species is a precursor of an active species for alkane oxidation.
- Hikichi, Shiro,Horii, Sena,Nakazawa, Jun,Okamura, Masaya,Terao, Ikumi
-
p. 6108 - 6118
(2020/05/25)
-
- A General Regioselective Synthesis of Alcohols by Cobalt-Catalyzed Hydrogenation of Epoxides
-
A straightforward methodology for the synthesis of anti-Markovnikov-type alcohols is presented. By using a specific cobalt triphos complex in the presence of Zn(OTf)2 as an additive, the hydrogenation of epoxides proceeds with high yields and selectivities. The described protocol shows a broad substrate scope, including multi-substituted internal and terminal epoxides, as well as a good functional-group tolerance. Various natural-product derivatives, including steroids, terpenoids, and sesquiterpenoids, gave access to the corresponding alcohols in moderate-to-excellent yields.
- Beller, Matthias,Junge, Kathrin,Leischner, Thomas,Li, Wu,Liu, Weiping
-
supporting information
p. 11321 - 11324
(2020/05/16)
-
- Erbium-Catalyzed Regioselective Isomerization-Cobalt-Catalyzed Transfer Hydrogenation Sequence for the Synthesis of Anti-Markovnikov Alcohols from Epoxides under Mild Conditions
-
Herein, we report an efficient isomerization-transfer hydrogenation reaction sequence based on a cobalt pincer catalyst (1 mol %), which allows the synthesis of a series of anti-Markovnikov alcohols from terminal and internal epoxides under mild reaction conditions (≤55 °C, 8 h) at low catalyst loading. The reaction proceeds by Lewis acid (3 mol % Er(OTf)3)-catalyzed epoxide isomerization and subsequent cobalt-catalyzed transfer hydrogenation using ammonia borane as the hydrogen source. The general applicability of this methodology is highlighted by the synthesis of 43 alcohols from epoxides. A variety of terminal (23 examples) and 1,2-disubstituted internal epoxides (14 examples) bearing different functional groups are converted to the desired anti-Markovnikov alcohols in excellent selectivity and yields of up to 98%. For selected examples, it is shown that the reaction can be performed on a preparative scale up to 50 mmol. Notably, the isomerization step proceeds via the most stable carbocation. Thus, the regiochemistry is controlled by stereoelectronic effects. As a result, in some cases, rearrangement of the carbon framework is observed when tri-and tetra-substituted epoxides (6 examples) are converted. A variety of functional groups are tolerated under the reaction conditions even though aldehydes and ketones are also reduced to the respective alcohols under the reaction conditions. Mechanistic studies and control experiments were used to investigate the role of the Lewis acid in the reaction. Besides acting as the catalyst for the epoxide isomerization, the Lewis acid was found to facilitate the dehydrogenation of the hydrogen donor, which enhances the rate of the transfer hydrogenation step. These experiments additionally indicate the direct transfer of hydrogen from the amine borane in the reduction step.
- Liu, Xin,Longwitz, Lars,Spiegelberg, Brian,T?njes, Jan,Beweries, Torsten,Werner, Thomas
-
p. 13659 - 13667
(2020/11/30)
-
- Ketone Hydrogenation by Using ZnO?Cu(OH)Cl/MCM-41 with a Splash of Water: An Environmentally Benign Approach
-
MCM-41-supported ZnO?Cu(OH)Cl nanoparticles were synthesized via an incipient wetness impregnation technique using zinc chloride and copper chloride salts as well as water at room temperature. The catalyst was characterized by powder X-ray diffraction (PXRD), infrared spectroscopy (IR), and TGA, whereas surface and morphological studies were performed by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The above studies revealed the incorporation of metal species into the pores of MCM-41, leading to a decrease in surface area of the nanoparticles that was found to be 239.079 m2/g. The substituents attached to the ketone determine the rate of the reaction, and the utilization of the green solvent ‘water’ astonishingly completes the hydrogenation reaction in 45 minutes at 40 °C with 100% conversion and 100% selectivity as analyzed by gas chromatography-mass spectrometry. Hence, ZnO?Cu(OH)Cl/MCM-41 nanoparticles with 2.46 wt% zinc and 6.39 wt% copper were demonstrated as an active catalyst for the reduction of ketones without using any gaseous hydrogen source making it highly efficient as well as environmentally and economically benign.
- Choudhary, Neha,Ghosh, Topi,Mobin, Shaikh M.
-
p. 1339 - 1348
(2020/03/23)
-
- Flexible NiCo-based catalyst for direct hydrodeoxygenation of guaiacol to cyclohexanol
-
The catalytic hydrodeoxygenation (HDO) of lignin-derived phenols is an important step for bio-oil upgrading. Herein, a novel HDO system was established in the presence of nitrogen, instead of traditional hydrogen. A series of CNT-supported Ni-based catalysts was prepared and introduced in the HDO of guaiacol and other lignin-derived phenolic compounds. The bimetallic NiCo/CNT catalysts exhibited better catalytic performance during the HDO reaction, in comparison with monometallic Ni/CNT and Co/CNT catalysts. Among these catalysts, the (15 + 5)% NiCo/CNT catalyst afforded the highest guaiacol conversion (up to 100%) with cyclohexanol as the main product in isopropanol. The effects of process parameters on guaiacol conversion and product distribution were studied in detail, finding that the presence of nitrogen could help to suppress the generation of byproducts, while the presence of hydrogen would facilitate the occurrence of side reactions. The HDO reaction of guaiacol occurred possibly in two consecutive steps: the demethoxylation of guaiacol to phenol and the further hydrogenation of the aromatic ring to cyclohexanol.
- Chen, Changzhou,Zhou, Minghao,Liu, Peng,Sharma, Brajendra K.,Jiang, Jianchun
-
p. 18906 - 18916
(2020/11/18)
-
- Direct Asymmetric Hydrogenation and Dynamic Kinetic Resolution of Aryl Ketones Catalyzed by an Iridium-NHC Exhibiting High Enantio- and Diastereoselectivity
-
A chiral iridium carbene-oxazoline catalyst is reported that is able to directly and efficiently hydrogenate a wide variety of ketones in excellent yields and good enantioselectivity (up to 93 % ee). Moreover, when using racemic α-substituted ketones, excellent diastereoselectivities were obtained (dr 99:1) by dynamic kinetic resolution of the in situ formed enolate. Overall, the herein described hydrogenation occurs under ambient conditions using low hydrogen pressures, providing a direct and atom efficient method towards chiral secondary alcohols.
- Ayya Swamy P, Chinna,Varenikov, Andrii,de Ruiter, Graham
-
supporting information
p. 2333 - 2337
(2020/02/11)
-
- Hydrogen-free ring hydrogenation of phenol to cyclohexanol over a rhodium-loaded titanium(IV) oxide photocatalyst
-
Since photocatalytic reactions are almost consistent with the concept of green chemistry, substance conversion using photocatalysts has recently attracted the attention of researchers in the fields of organic chemistry, physical chemistry and material chemistry. We investigated photoinduced ring hydrogenation of phenol over a metal-loaded titanium(IV) oxide (TiO2) photocatalyst without the use of H2 gas and we report here the effects of various parameters, including the type and amount of metal co-catalyst loaded on TiO2 and the kinds of solvents and hole scavengers, on the ring hydrogenation. We found that the combination of an Rh co-catalyst, water and oxalic acid resulted in the highest yield of cyclohexanol. Detailed analyses revealed that phenol was first hydrogenated to cyclohexanone via keto-enol tautomerism of cyclohexenol followed by hydrogenation of cyclohexanone to cyclohexanol and that adsorption of phenol onto Rh-TiO2 is a factor of great importance for the ring hydrogenation.
- Kinoshita, Atsufumi,Nakanishi, Kousuke,Yagi, Ryosuke,Tanaka, Atsuhiro,Hashimoto, Keiji,Kominami, Hiroshi
-
-
- Mont-K10 Supported Fe(II) Schiff-Base Complex as an Efficient Catalyst for Hydrogenation of Ketones
-
Abstract: A new Fe(II) Schiff base complex anchored on mont-K10 (Fe@imine-mont-K10) was synthesized and extensively characterized by FTIR, powder X-ray diffraction, SEM–EDX, TEM, ESR, X-ray photoelectron spectroscopy (XPS), BET surface area measurement, solid state 29Si NMR and ICP-AES analysis. The catalytic activity of the complex was investigated for hydrogenation of ketones. The results indicated that it exhibited good catalytic activity for hydrogenation of aromatic as well as aliphatic ketones in i-PrOH/CH3CN (1:1) using Na-i-OPr as base at 80?°C resulting in moderate to excellent isolated yields (51–99%) of their corresponding products. The catalyst shows good reusability. Graphical Abstract: [Figure not available: see fulltext.].
- Sultana, Samim,Borah, Geetika,Gogoi, Pradip. K.
-
p. 2142 - 2157
(2019/05/28)
-
- Transfer hydrogenation of ketones catalyzed by a trinuclear Ni(II) complex of a Schiff base functionalized N-heterocyclic carbene ligand
-
A new Schiff base-functionalized N-heterocyclic carbene ligand precursor 3-benzyl-1-[2-((2-hydroxy-benzylidene)-amino]-ethyl-3H-imidazol-1-ium bromide (3), and its trinuclear Ni(II) complex [LNiL-Ni-LNiL].2Br (4) where L = 2-[2-(3-benzylimidazol-1-yl) ethyliminomethyl]phenol, were synthesized via the solventless and free carbene routes respectively. Both compounds were characterized by spectroscopic and X-ray diffraction techniques. Single crystal XRD analysis of 4 showed that it is composed of a central square planar Ni(II) ion symmetrically linked to two distorted square planar Ni(II) ions via two bridging ligands. The central Ni(II) ion is only bound to the Schiff base moieties of the bridging ligands via the phenolate oxygen donor (O1) and imine nitrogen donor (N1) atoms in a trans [N^O^(Ni2+)^N^O] mode, whilst the carbene moieties of each bridging ligand and a tridentate L are coordinated in a distorted square planar CNHC-(Ni2+)^N^O^CNHC mode to stabilise each of the terminal Ni(II) ions. Complex 4 showed significant activity as a catalyst in the transfer hydrogenation of a range of aliphatic and aromatic ketones, at a catalyst concentration of 0.1 mol%. An excellent conversion up to 100% was achieved for aromatic ketones after 4 h.
- Abubakar, Samaila,Ibrahim, Halliru,Bala, Muhammad D.
-
p. 276 - 282
(2018/10/02)
-
- SN2 Reaction of Diarylmethyl Anions at Secondary Alkyl and Cycloalkyl Carbons
-
The substitution reaction of the diethyl allylic and propargylic phosphates with Ar2CH anions was applied to sec-alkyl phosphates to compare reactivity and stereoselectivity. However, the substitution took place on the ethyl carbon of the diethyl phosphate group. We then found that the diphenyl phosphate leaving group ((PhO)2PO2) was suited for the substitution at the sec-alkyl carbon. Enantioenriched diphenyl sec-alkyl phosphates with different substituents (Me, Et, iPr) on the vicinal position underwent the substitution reaction with almost complete inversion (>99% enantiospecificity). The substitution reactions of cyclohexyl phosphates possessing cis or trans substituents (Me and/or tBu) at the C4, C3, and C2 positions of the cyclohexane ring were also studied to observe the difference in reactivity among the cis and trans isomers. A transition-state model with the phosphate leaving group ((PhO)2PO2) in the axial position was proposed to explain the difference. This model was supported by computational calculation of the virtual substitution reaction of the structurally simpler “dimethyl” cyclohexyl phosphates (leaving group = (MeO)2PO2) with MeLi. Furthermore, the calculation unexpectedly indicated higher propensity of (PhO)2PO2 as a leaving reactivity than alkyl phosphate groups such as (MeO)2PO2 and (iPrO)2PO2.
- Shinohara, Riku,Ogawa, Narihito,Kawashima, Hidehisa,Wada, Kyohei,Saito, Shun,Yamazaki, Takashi,Kobayashi, Yuichi
-
p. 1461 - 1478
(2019/01/25)
-
- New copper(II) coordination compounds assembled from multifunctional pyridine-carboxylate blocks: Synthesis, structures, and catalytic activity in cycloalkane oxidation
-
Two new copper(II) coordination compounds, namely a 1D coordination polymer [Cu(μ-cpna)(phen)(H2O)]n (1) and a discrete tetracopper(II) derivative [Cu(phen)2(H2O)]2[Cu2(μ-Hdppa)2(Hdppa)2] (2), were hydrothermally synthesized from copper(II) chloride as a metal source, 5-(4-carboxyphenoxy)nicotinic acid (H2cpna) or 5-(3,4-dicarboxylphenyl)picolinic acid (H3dppa) as a principal building block, and 1,10-phenanthroline (phen) as a crystallization mediator. Compounds 1 and 2 were isolated as air-stable microcrystalline solids and fully characterized by elemental and thermogravimetric analyses, IR spectroscopy, powder and single-crystal X-ray diffraction. In the solid state, the structure of 1 discloses the linear interdigitated 1D coordination polymer chains with the 2C1 topology. The crystal structure of an ionic derivative 2 shows that the mono-and dicopper(II) units are extended into the intricate 1D hydrogen-bonded chains with the SP 1-periodic net (4,4)(0,2) topology. Thermal stability and catalytic properties of 1 and 2 were also investigated. In fact, both Cu derivatives act as efficient homogeneous catalysts (catalyst precursors) for the mild oxidation of cycloalkanes by hydrogen peroxide to give the corresponding alcohols and ketones; the substrate scope and the effects of type and amount of acid promoter as well as bond-, regio-, and stereo-selectivity features were investigated.
- Zhao, Na,Li, Yu,Gu, Jinzhong,Fernandes, Tiago A.,Kirillova, Marina V.,Kirillov, Alexander M.
-
supporting information
(2019/01/14)
-
- Highly Selective and Catalytic Oxygenations of C?H and C=C Bonds by a Mononuclear Nonheme High-Spin Iron(III)-Alkylperoxo Species
-
The reactivity of a mononuclear high-spin iron(III)-alkylperoxo intermediate [FeIII(t-BuLUrea)(OOCm)(OH2)]2+(2), generated from [FeII(t-BuLUrea)(H2O)(OTf)](OTf) (1) [t-BuLUrea=1,1′-(((pyridin-2-ylmethyl)azanediyl)bis(ethane-2,1-diyl))bis(3-(tert-butyl)urea), OTf=trifluoromethanesulfonate] with cumyl hydroperoxide (CmOOH), toward the C?H and C=C bonds of hydrocarbons is reported. 2 oxygenates the strong C?H bonds of aliphatic substrates with high chemo- and stereoselectivity in the presence of 2,6-lutidine. While 2 itself is a sluggish oxidant, 2,6-lutidine assists the heterolytic O?O bond cleavage of the metal-bound alkylperoxo, giving rise to a reactive metal-based oxidant. The roles of the urea groups on the supporting ligand, and of the base, in directing the selective and catalytic oxygenation of hydrocarbon substrates by 2 are discussed.
- Ghosh, Ivy,Banerjee, Sridhar,Paul, Satadal,Corona, Teresa,Paine, Tapan Kanti
-
p. 12534 - 12539
(2019/08/07)
-
- Continuous-Flow Palladium-Catalyzed Synthesis of Cyclohexanones from Phenols using Sodium Formate as a Safe Hydrogen Source
-
We report a procedure for the continuous-flow production of cyclohexanone from phenol on the basis of the use of sodium formate as a biomass-derived source of hydrogen and Pd/C as an easily accessible catalyst system. The reaction worked in water at pH 12.0 at 90 °C. By setting a packed reactor charged with the Pd/C catalyst (10 wt %) at a flow rate of 0.5 mL min?1, we achieved continuous-flow production of cyclohexanone in high yield with high selectivity and productivity.
- Valentini, Federica,Santillo, Niccolò,Petrucci, Chiara,Lanari, Daniela,Petricci, Elena,Taddei, Maurizio,Vaccaro, Luigi
-
p. 1277 - 1281
(2018/02/23)
-
- Synthesis and Catalytic Activity of (3,4-Diphenylcyclopentadienone)Iron Tricarbonyl Compounds in Transfer Hydrogenations and Dehydrogenations
-
Four (3,4-diphenylcyclopentadienone)iron tricarbonyl compounds were synthesized, and their activities in transfer hydrogenations of carbonyl compounds and transfer dehydrogenations of alcohols were explored and compared to those of the well-established [2,5-(SiMe3)2-3,4-(CH2)4(η4-C4C=O)]Fe(CO)3 (3). A new compound, [2,5-bis(3,5-dimethylphenyl)-3,4-diphenylcyclopentadienone]iron tricarbonyl (7), was the most active catalyst in both transfer hydrogenations and dehydrogenations, and compound 3 was the least active catalyst in transfer hydrogenations. Evidence was found for product inhibition of both 3 and 7 in a transfer dehydrogenation reaction, with the activity of 3 being more heavily affected. A monomeric iron hydride derived from 7 was spectroscopically observed during a transfer hydrogenation, and no diiron bridging hydrides were found under reductive or oxidative conditions. Initial results in the transfer hydrogenation of N-benzylideneaniline showed that 3 was a significantly less active catalyst in comparison to the (3,4-diphenylcyclopentadienone)iron tricarbonyl compounds.
- Funk, Timothy W.,Mahoney, Andrew R.,Sponenburg, Rebecca A.,Zimmerman, Kathryn P.,Kim, Daniel K.,Harrison, Emily E.
-
supporting information
p. 1133 - 1140
(2018/04/17)
-
- Application of Ni(II) complexes of air stable Schiff base functionalized N-heterocyclic carbene ligands as catalysts for the transfer hydrogenation of aliphatic ketones
-
New air stable N-heterocyclic carbene functionalized Schiff base ligands (L) of the type 2-[-2-[3-(R)imidazol-1-yl]ethyliminomethyl]phenol [R = methyl (2), 2-pyridylmethyl (3)] were synthesized and characterized by NMR, IR, MS, and CHN analysis. Single crystal X-ray structural analysis of their Ni(II) complexes revealed square planar arrangement of the chelating ligands coordinated in tridentate (2, C^N^O) and tetradentate (3, N^C^N^O) modes around the metal. The three new isolated and fully characterized complexes were utilized as catalysts for the catalytic transfer hydrogenation of aliphatic ketones in 2-propanol as solvent and source of hydrogen. Based on 0.2 mol% catalyst concentration, the complexes showed activity for aliphatic ketones and 100% conversion (turnover number of 500) for cyclohexanone and all the aromatic ketones tested.
- Abubakar, Samaila,Bala, Muhammad D.
-
p. 2913 - 2923
(2018/09/27)
-
- Interplay between Substrate and Proton Donor Coordination in Reductions of Carbonyls by SmI2-Water Through Proton-Coupled Electron-Transfer
-
The reduction of a carbonyl by SmI2-water is the first step in a range of reactions of synthetic importance. Although the reduction is often proposed to proceed through an initial stepwise electron-transfer-proton-transfer (ET-PT), recent work has shown that carbonyls and related functional groups are likely reduced though proton-coupled electron-transfer (PCET). In the present work, the reduction of an activated ester, aldehyde, a linear and cyclic ketone, and related sterically demanding carbonyls by SmI2-H2O was examined through a series of mechanistic experiments. Kinetic studies demonstrate that all substrates exhibit significant increases in the rate of reduction by SmI2 as [H2O] is increased. Under identical conditions, ketones and an aldehyde containing a methyl adjacent to the carbonyl are reduced slower than an unsubstituted variant by an order of magnitude, demonstrating the importance of substrate coordination. In the case of unactivated substrates, rates of reduction show excellent correlation with the calculated bond dissociation free energy of the O-H bond of the intermediate ketyl and the calculated free energy of intermediate ketyl radical anions derived from unhindered substrates: findings consistent with concerted PCET. Activated esters derived from methylbenzoate are likely reduced through stepwise or asynchronous PCET. Overall, this work demonstrates that the combination of the coordination of substrate and water to Sm(II) provides a configuration uniquely suited to a coupled electron- and proton-transfer process.
- Chciuk, Tesia V.,Anderson, William R.,Flowers, Robert A.
-
supporting information
p. 15342 - 15352
(2018/11/30)
-
- Hydrogenolysis of lignin model compounds into aromatics with bimetallic Ru-Ni supported onto nitrogen-doped activated carbon catalyst
-
Lignin is the most abundant and renewable resources for production of natural aromatics. In this paper, new bimetallic catalytic system of Ru and Ni supported onto nitrogen-doped activated carbon (Ru-Ni-AC/N) was developed and its performances on hydrogenolysis of lignin model compounds under mild reaction conditions (1.0 MPa, 230 °C, in aqueous) were investigated. The results indicate that Ru-Ni-AC/N was a highly active, selective and stable catalyst for the conversion of lignin model compounds into aromatics, e.g. phenol, benzene and their derivatives. As verified by BET, XRD, HRTEM, XPS, H2-TPR and ICP-MS, the strong synergistic effects between i) Ru and Ni and ii) metals and N-groups were contributed to its excellent aromatics selectivity. What's more, the introduction of electron rich N atoms on AC was beneficial to the stabilization of metal particles, which greatly enhanced the durability of the catalyst.
- Hu, Yinghui,Jiang, Guangce,Xu, Guoqiang,Mu, Xindong
-
p. 316 - 326
(2018/01/05)
-
- Ductile Pd-Catalysed Hydrodearomatization of Phenol-Containing Bio-Oils Into Either Ketones or Alcohols using PMHS and H2O as Hydrogen Source
-
A series of phenolic bio-oil components were selectively hydrodearomatized by palladium on carbon into the corresponding ketones or alcohols in excellent yields using polymethylhydrosiloxane and water as reducing agent. The selectivity of the reaction was governed by the water concentration where selectivity to alcohol was favoured at higher water concentrations. As phenolic bio-oil examples cardanol and beech wood tar creosote were studied as substrate to the developed reaction conditions. Cardanol was hydrodearomatized into 3-pentadecylcyclohexanone in excellent yield. From beech wood tar creosote, a mixture of cyclohexanols was produced. No hydrodeoxygenation occurred, suggesting the applicability of the reported method for the production of ketone-alcohol oil from biomass. (Figure presented.).
- Di Francesco, Davide,Subbotina, Elena,Rautiainen, Sari,Samec, Joseph S. M.
-
supporting information
p. 3924 - 3929
(2018/09/14)
-
- Bioinspired Olefin cis-Dihydroxylation and Aliphatic C-H Bond Hydroxylation with Dioxygen Catalyzed by a Nonheme Iron Complex
-
A mononuclear iron(II)-α-hydroxy acid complex [(TpPh,Me)FeII(benzilate)] (TpPh,Me = hydrotris(3-phenyl-5-methylpyrazol-1-yl)borate) of a facial tridentate ligand has been isolated and characterized to explore its catalytic efficiency for aerial oxidation of organic substrates. In the reaction between the iron(II)-benzilate complex and O2, the metal-coordinated benzilate is stoichiometrically converted to benzophenone with concomitant reduction of dioxygen on the iron center. Based on the results from interception experiments and labeling studies, different iron-oxygen oxidants are proposed to generate in situ in the reaction pathway depending upon the absence or presence of an external additive (such as protic acid or Lewis acid). The five-coordinate iron(II) complex catalytically cis-dihydroxylates olefins and oxygenates the C-H bonds of aliphatic substrates using O2 as the terminal oxidant. The iron(II) complex exhibits better catalytic activity in the presence of a Lewis acid.
- Chatterjee, Sayanti,Bhattacharya, Shrabanti,Paine, Tapan Kanti
-
p. 10160 - 10169
(2018/08/28)
-
- Ni3P as a high-performance catalytic phase for the hydrodeoxygenation of phenolic compounds
-
The catalytic performance of an unsupported Ni2P in the aqueous phase hydrodeoxygenation (HDO) of phenol was investigated. It was found that the unsupported Ni2P was water-sensitive, being transformed stepwise, first to an amorphous phase and then to Ni5P2 and Ni12P5, and finally to Ni3P in the presence of water at elevated temperatures. Nonetheless, the generated Ni3P phase exhibited extraordinary hydrogenation activity at low temperatures and high HDO activity at high temperatures. The unsupported Ni3P was more active for the hydrogenation of the aromatic ring in the phenol molecule than Pd/SiO2 (1.0 wt%). The unsupported Ni3P was catalytically active and stable in phenol HDO in both the aqueous phase and the organic phase. In addition to phenol, catechol and o-cresol were investigated in the HDO catalyzed by the unsupported Ni3P in both aqueous solution and decalin solution. The HDO reactivity decreased in the order of phenol > catechol > o-cresol in the aqueous phase, and in the order of phenol > o-cresol in the organic phase (catechol is insoluble in decalin). In the oil phase HDOs of phenol and o-cresol, the unsupported Ni3P exhibited superior hydrogenation activity to that of the unsupported Ni2P at low temperatures.
- Yu, Zhiquan,Wang, Yao,Sun, Zhichao,Li, Xiang,Wang, Anjie,Camaioni, Donald M.,Lercher, Johannes A.
-
supporting information
p. 609 - 619
(2018/02/14)
-
- Synergetic Catalysis of Nickel Oxides with Oxygen Vacancies and Nickel Phosphide for the Highly Efficient Hydrodeoxygenation of Phenolic Compounds
-
The highly efficient hydrodeoxygenation of oxygenated chemicals at a low temperature is a critical issue for biomass crude oil upgrading to reduce equipment and operation expense. The unique electronic features of oxygen vacancies have been found to facilitate deoxygenation above 250 °C. In this work, a series of NiOx/SiO2 catalysts that contain oxygen vacancies was prepared by a sol–gel and controllable temperature-programmed reduction method. Results show that NiOx/SiO2 has a superior phenol hydrogenation activity in deoxygenation even at 180 °C to Ni2P/SiO2. The high hydrogenation activity derives from the flat adsorption of phenolics over low-valence Ni cations induced by connected oxygen vacancies. After the introduction of NiOx into Ni2P catalysts, composite NiOx-Ni2P/SiO2 (0.43≤x2P and NiOx catalysts and most catalysts presented previously because the coexistence of oxygen vacancies from NiOx and the acidity induced by Ni2P results in the synergistic effect of the adsorption configuration and hydrodeoxygenation ability. Besides, this composite catalyst also has a high activity for the hydrodeoxygenation of different bio-derived cresol isomers. The reuse test results confirm that oxygen vacancies are relatively stable in comparison with the phosphide.
- Li, Yunhua,Zhao, Yafei,Chen, Binghui,Wang, Wenju
-
p. 2612 - 2619
(2018/06/26)
-
- Half-Sandwich Osmium(II) Complexes with Bidentate N,N-Chelating Ligands and Their Use in the Transfer Hydrogenation of Ketones
-
The reaction of appropriate N,N-bidentate ligands with the [(η6-p-cymene)Os(μ-Cl)Cl]2dimer (p-cymene = C10H14), followed by metathesis reaction with NH4PF6, gave the new osmium(II) arene complex salts [(η6-p-cymene)OsCl(C5H4N-2-CH=N–R)]PF6, where [R = tert-butyl (1), isopropyl (2), 2,6-dimethylphenyl (3), or 2,6-diisopropylphenyl (4)]. The dimer was also reacted with the N,N′-bidentate ligands di-(2-pyridyl)amine (5), 4-phenyl-3,6-di(2-pyridyl)pyridazine (6), 4,4′-di-tert-butyl-2, 2′-bipyridine (7), and 5,5′-dimethyl-2,2′-bipyridine (8). In addition, the reaction of the precursor [(η6-C6H6)Os(μ-Cl)Cl]2with the N,N′-bidentate ligands gave [(η6-C6H6)OsCl(N,N)]2where N,N = 4,4′-di-tert-butyl-2,2′-bipyridine (9), 5,5′-dimethyl-2,2′-bipyridine (10), 3,6-bis(2-pyridyl)-4-phenyl pyridazine (11), or di-(2-pyridyl)amine (12). The compounds were characterized by using1H and13C NMR, UV/Vis, FTIR spectroscopy and elemental analysis. The single-crystal X-ray structures for compounds 1, 4, 8, 10, 11, and 12 showed that the osmium(II) complexes adopted the classical three-legged piano stool geometry. These osmium(II) compounds were found to be effective catalysts for the transfer hydrogenation of ketones into alcohols with NaOH as base and 2-propanol as the solvent and hydrogen source. A range of cyclic, aromatic, and aliphatic ketones was studied and good turnover numbers achieved.
- Gichumbi, Joel M.,Omondi, Bernard,Friedrich, Holger B.
-
p. 915 - 924
(2017/02/15)
-
- Orientation towards asymmetric transfer hydrogenation of ketones catalyzed by (pyrazolyl)ethyl)pyridine Fe(II) and Ni(II) complexes
-
Compounds 2-[1-(3,5-dimethylpyrazol-1-yl)ethyl]pyridine (L1) and 2-[1-(3,5-diphenylpyrazol-1-yl)ethyl]pyridine (L2) were obtained in a three-step procedure which involved the reduction of acetylpyridine using NaBH4, chlorination of the alcohol intermediate using SOCl2 and subsequent reaction with appropriate pyrazoles. Reactions of L1 and L2 with Ni(II) and Fe(II) halides produced the respective complexes Ni(L1)Br2 (1), Ni(L1)Cl2 (2), Fe(L1)Cl2 (3) and Ni(L2)Br2 (4) as racemic mixtures in moderate yields. The molecular structures of complexes 1 and 4 are dinuclear and mononuclear respectively. All the complexes (1–4) formed active catalysts for the transfer hydrogenation of ketones (THK) in 2-propanol at 82?°C affording conversions of 58%–84% within 48?h. The influence of catalyst structure, reaction conditions and identity of ketone substrates in the TH reactions have been successfully established.
- Magubane, Makhosazane N.,Alam, Mohd Gulfam,Ojwach, Stephen O.,Munro, Orde Q.
-
p. 197 - 201
(2017/02/18)
-
- Reversibility of Ketone Reduction by SmI2-Water and Formation of Organosamarium Intermediates
-
The reduction of ketones by SmI2-water has long been thought to proceed through a reversible initial electron transfer with the formation of organosamarium intermediates in a follow-up step. Kinetic experiments on the reduction of two model ketones and structurally similar ketones with a pendant alkene are shown to be consistent with a rate-limiting reduction by SmI2-water through a proton-coupled electron-transfer (PCET). Literature values for the rates of radical cyclizations and reduction of radicals by SmI2 and thermochemical data for radical reduction by SmI2-water further support a rate-limiting initial step for ketone reductions. These data suggest that discrete organosamarium species may not be intermediates in ketone reductions by SmI2-water.
- Chciuk, Tesia V.,Anderson, William R.,Flowers, Robert A.
-
p. 4579 - 4583
(2017/12/18)
-
- Method for preparing 2-methyl cyclohexanol by performing catalytic hydrogenation on orthocresol
-
The invention discloses a method for preparing 2-methyl cyclohexanol by performing catalytic hydrogenation on orthocresol, belonging to the technical field of orthocresol synthesis. The method comprises the following step: carrying out reaction on orthocresol and hydrogen in a hydrogenation reactor under the action of a ruthenium-base catalyst under heating conditions to generate the 2-methyl cyclohexanol, wherein the ruthenium-base catalyst is a supported catalyst which uses metal ruthenium as an active component and a composite metal oxide as a support, and no solvent is added into the reaction system. By using the composite metal oxide as the support, the method has the advantages of mild reaction conditions, high reaction efficiency, no need of any organic solvent, low catalyst consumption, low investment, low production cost, fewer byproducts, simple technique and the like, and is suitable for industrialized popularization and application.
- -
-
Paragraph 0021-0041
(2017/07/19)
-
- A method for synthesis of substituted cyclohexanol
-
The invention discloses a substituted cyclohexanol synthesis method. The substituted cyclohexanol synthesis method comprises that a phenolic compound as a raw material undergoes a one-step reaction in the presence of an amorphous alloy as a catalyst in a water phase to produce substituted cyclohexanol. The substituted cyclohexanol synthesis method is free of an organic solvent, has environmental friendliness, realizes high activity and high selectivity conversion of a phenolic compound into substituted cyclohexanol, has low energy consumption, is convenient for operation and prevents carbon deposition-caused catalyst deactivation.
- -
-
Paragraph 0039; 0040; 0042; 0044
(2017/08/25)
-
- Catalytic carbonyl hydrosilylations: Via a titanocene borohydride-PMHS reagent system
-
Reduction of a wide range of aldehydes and ketones with catalytic amounts of titanocene borohydride in concert with a stoichiometric poly(methylhydrosiloxane) (PMHS) reductant is reported. Preliminary mechanistic studies demonstrate that the reaction is mediated by a reactive titanocene(iii) complex, whose oxidation state remains constant throughout the reaction.
- Fianu, Godfred D.,Schipper, Kyle C.,Flowers, Robert A.
-
p. 3469 - 3473
(2017/08/21)
-
- Preparation and application of surface activated Si-MCM-41 and SBA-16 as reusable supports for reduction of cyclic ketones with preferential stereoselectivity
-
An efficient and benign procedure for the reduction of a few cyclic ketones adsorbed on the activated surface of calcined Si-MCM-41 and calcined SBA-16 using NaBH4 as the reducing agent with ethanol as the medium resulted in the formation of two epimeric alcohols. After synthesis, these calcined materials were treated with concentrated HCl to activate surface silanol groups. Various instrumental techniques like FTIR, XRD, N2 sorption isotherms, FESEM, TEM and XPS were carried out to examine the pre and post activated surface of the used supports. Five cyclic ketones were reduced. Reduction of 4-tert-butylcyclohexanone yielded only trans-4-tert-butylcyclohexanol. Moreover, exclusive formation of cis-3-methylcyclohexanol (equatorial -OH) was also observed. This work offers several advantages such as a simple operational procedure, short reaction time, and high yield of the product, along with maintaining the materials' diversity. This is due to the presence of the activated silanol groups of these materials, which cause nucleophilic activation of the carbonyl group of ketones leading to faster reaction rates. Beside this, these supports can be regenerated well from the reaction mixture using a calcination treatment followed by concentrated HCl, and reused several times without causing any serious malformation in the activated surfaces. Finally, this work opens up a new direction of research for the fabrication of solid reusable supports in the reduction of cyclic ketones.
- Chaudhuri, Haribandhu,Dash, Subhajit,Sarkar, Ashis
-
p. 99444 - 99454
(2016/11/02)
-
- Synthesis and characterization of half-sandwich ruthenium(II) complexes with N-alkyl pyridyl-imine ligands and their application in transfer hydrogenation of ketones
-
A series of new arene ruthenium(II) complexes were prepared by reaction of ruthenium(II) precursors of the general formula [(η6-arene)Ru(μ-Cl)Cl]2 with N,N′-bidentate pyridyl-imine ligands to form complexes of the type [(η6-arene)RuCl(C5H4N-2-CH=N-R)]PF6, with arene?=?C6H6, R?=?iso-propyl (1a), tert-butyl (1b), cyclohexyl (1c), cyclopentyl (1d) and n-butyl (1e); arene?=?p-cymene, R?=?iso-propyl (2a), tert-butyl (2b). The complexes were fully characterized by 1H NMR and 13C NMR, UV–Vis and IR spectroscopies, elemental analyses, and the single-crystal X-ray structures of 2a and 2b have been determined. The single-crystal molecular structure revealed both compounds with a pseudo-octahedral geometry around the Ru(II) center, normally referred to as a piano stool conformation, with the pyridyl-imine as a bidentate N,N ligand. The activity of all complexes in the transfer hydrogenation of cyclohexanone in the presence of NaOH and iso-propanol is reported, the compounds showing turnover numbers of close to 1990 and high conversions. Complex 2b was also shown to be very effective for a range of aliphatic and cyclic ketones, giving conversions of up to 100?%.
- Gichumbi, Joel M.,Friedrich, Holger B.,Omondi, Bernard
-
p. 867 - 877
(2016/10/25)
-
- Application of arene ruthenium(II) complexes with pyridine-2-carboxaldimine ligands in the transfer hydrogenation of ketones
-
The reaction of various pyridine-2-carboxaldimine ligands with the [(η6-arene)Ru(μ-Cl)Cl]2 dimer followed by a metathesis reaction with ammonium hexaflourophosphate, yielded the ruthenium(II) arene complex salts [(η6-arene)RuCl(C5H4[Formula presented]6; where (arene?=?C6H6 (1), p-cymene (2), Ar?=?3, 5-dimethyl phenyl (a), 2,3-dimethyl phenyl (b), 2,5-dimethyl phenyl (c), 3,4-dimethyl phenyl (d)). The compounds were characterized by elemental analysis, FT- IR, UV–vis and 1H and 13C NMR. Single crystal X-ray structures for compounds 1a, 1d and 2e were also determined and showed that the ruthenium(II) centre has a pseudo-octahedral geometry and the molecule adopted a three legged piano stool geometry in which the arene ring occupies the apex and the nitrogen atoms of the N,N′-bidentate ligand and the chloride atom the base of the stool. The Ru(II) complex salts were active for the catalytic transfer hydrogenation of ketones into alcohols in the presence of NaOH using 2-propanol as the hydrogen source at 82?°C. The complexes were suitable for a wide range of aliphatic, cyclic and aromatic ketones giving good turn over numbers.
- Gichumbi, Joel M.,Friedrich, Holger B.,Omondi, Bernard
-
-
- Alcohol oxidation with H2O2 catalyzed by a cheap and promptly available imine based iron complex
-
We previously reported that the iminopyridine iron(II) complex 1, easily and quantitatively obtainable in situ, can activate H2O2 to form a powerful oxidant, capable of aliphatic C-H bond hydroxylation. In the present study we expand the application of this catalyst to the oxidation of a series of alcohols to the corresponding carbonyl compounds. The oxidation of aliphatic alcohols proceeds smoothly, while that of benzylic alcohols is shown to be challenging. Some collected pieces of evidence suggest a preference of the oxidizing species for the aromatic ring instead for the alcoholic moiety. The decrease of the electron density in the aromatic ring shifts the oxidation from the aromatic towards the alcoholic moiety. Quite surprisingly, preferential oxidation of cyclohexanol versus benzylic alcohol was achieved, showing unprecedented selectivity.
- Olivo, Giorgio,Giosia, Simone,Barbieri, Alessia,Lanzalunga, Osvaldo,Di Stefano, Stefano
-
supporting information
p. 10630 - 10635
(2016/11/21)
-
- Upgrading of aromatic compounds in bio-oil over ultrathin graphene encapsulated Ru nanoparticles
-
Fast pyrolysis of biomass for bio-oil production is a direct route to renewable liquid fuels, but raw bio-oil must be upgraded in order to remove easily polymerized compounds (such as phenols and furfurals). Herein, a synthesis strategy for graphene encapsulated Ru nanoparticles (NPs) on carbon sheets (denoted as Ru@G-CS) and their excellent performance for the upgrading of raw bio-oil were reported. Ru@G-CS composites were prepared via the direct pyrolysis of mixed glucose, melamine and RuCl3 at varied temperatures (500-800 °C). Characterization indicated that very fine Ru NPs (2.5 ± 1.0 nm) that were encapsulated within 1-2 layered N-doped graphene were fabricated on N-doped carbon sheets (CS) in Ru@G-CS-700 (pyrolysis at 700 °C). And the Ru@G-CS-700 composite was highly active and stable for hydrogenation of unstable components in bio-oil (31 samples including phenols, furfurals and aromatics) even in aqueous media under mild conditions. This work provides a new protocol to the utilization of biomass, especially for the upgrading of bio-oil.
- Shi, Juanjuan,Zhao, Mengsi,Wang, Yingyu,Fu, Jie,Lu, Xiuyang,Hou, Zhaoyin
-
supporting information
p. 5842 - 5848
(2016/05/24)
-
- Aromatic ring hydrogenation catalysed by nanoporous montmorillonite supported Ir(0)-nanoparticle composites under solvent free conditions
-
Ir(0)-nanoparticles (Ir-NPs) were synthesized into the nanopores of modified montmorillonite clay by incipient wetness impregnation of IrCl3 followed by reduction with ethylene glycol. The activation of the montmorillonite clay was carried out by treatment with HCl under controlled conditions to increase the surface area by generating nanopores which act as host for the metal nanoparticles. The synthesized Ir-NP-montmorillonite composites were characterized by N2-sorption, powder XRD, SEM, EDS, TEM, XPS, etc. The composites exhibit high surface area of 327 m2 g-1 and the Ir-NPs with size around 4 nm are uniformly distributed on the support. The Ir-NPs show efficient catalytic activity in aromatic ring hydrogenation under solvent free conditions with maximum conversion up to 100% and Turn Over Frequency (TOF) up to 79 h-1. The catalyst can be easily separated by simple filtration and remained active for several runs without significant loss of catalytic efficiency.
- Das, Prabin,Sarmah, Podma Pollov,Borah, Bibek Jyoti,Saikia, Lakshi,Dutta, Dipak Kumar
-
p. 2850 - 2855
(2016/03/22)
-
- Mapping reactivities of aromatic models with a lignin disassembly catalyst. Steps toward controlling product selectivity
-
Copper-doped porous metal oxides catalyze the one-pot disassembly of biomass-derived lignin via C-O bond hydrogenolysis and hydrodeoxygenation in supercritical methanol. This catalytic system cleanly converts lignin as well as lignocellulose composites, such as sawdust, to organic liquids with little or no formation of intractable tars or chars. However, this catalyst based on Earth-abundant components also catalyzes less desirable aromatic ring hydrogenations and various methylations that contribute to the diversity of products. In this context, we undertook a quantitative experimental and computational evaluation of model reactions relevant to the reductive disassembly of lignin by this catalyst system in order to determine quantitatively the rates of desirable and less desirable chemical steps that define the overall product selectivities. Global fitting analysis methods were used to map the temporal evolution of key intermediates and products and to elucidate networks that provide guidelines regarding the eventual fates of reactive intermediates in this catalysis system. Phenolic compounds display multiple reaction pathways, but substrates such as benzene, toluene, and alkyl- and alkoxy-substituted aromatics are considerably more stable under these conditions. These results indicate that modifying this catalytic system in a way that controls and channels the reactivity of phenolic intermediates should improve selectivity toward producing valuable aromatic chemicals from biomass-derived lignin. To this end we demonstrate that the O-methylating agent dimethyl carbonate can intercept the phenol intermediate formed from hydrogenolysis of the model compound benzyl phenyl ether. Trapping the phenol as anisole thus gave much higher selectivity towards aromatic products.
- Bernt, Christopher M.,Bottari, Giovanni,Barrett, Jacob A.,Scott, Susannah L.,Barta, Katalin,Ford, Peter C.
-
p. 2984 - 2994
(2016/05/24)
-
- 2-methyl cyclohexyl acetate method for the synthesis of (by machine translation)
-
The invention discloses a 2-methyl cyclohexyl acetic acid ester synthetic method, including (1) hydrogenation reaction: the O-cresol in dissolved in methyl cyclohexane, then adding hydrogenation catalyst and high purity hydrogen, after the hydrogenation reaction, with 2-methyl-cyclohexanol of a hydrogenation reaction liquid ; (2) the esterification reaction: the hydrogenation reaction of esterification catalyst and the liquid are added to a reaction vessel, using acetic acid as the esterifying agent, stirring the mixed solution is dropped to the central area, to undergo esterification reaction, to obtain 2-methyl cyclohexyl acetate. The synthetic method of this invention can effectively improve the 2-methyl cyclohexyl acetate synthetic yield, fixed asset investment is reduced, the running cost is reduced, simplifying the production process complexity. (by machine translation)
- -
-
Paragraph 0075-0079
(2017/03/18)
-
- Conjugated polymeric metal porphyrin for catalytic oxidation of alkanes and cycloalkanes method
-
The invention discloses a method for catalyzing air or oxygen to oxidize alkane and cycloparaffin by use of conjugated polymetalloporphyrin. Solid polymetalloporphyrin which has high porosity and specific surface area and is formed by coupling and polymerizing conjugated alkynyl is used as a catalyst for catalytic oxidation of hydrocarbon bonds of the alkane and the cycloparaffin under a gentle condition so as to obtain a corresponding oxidation product such as ketonic acid and the like. The amount of the used catalyst is small, and the catalytic effect is good. The catalyst is not dissolved or decomposed in a reaction system and can be recycled for lots of times. The transformation rate of the hydrocarbon bonds in catalytic oxidation is high and good alcohol ketone selectivity is achieved.
- -
-
Paragraph 0024; 0025
(2017/02/09)
-
- Transfer hydrogenation of unsaturated bonds in the absence of base additives catalyzed by a cobalt-based heterogeneous catalyst
-
A novel non-noble Co@C-N catalytic system has been developed for catalytic transfer hydrogenation reactions. Co@C-N was found to be highly active and selective in the hydrogenation of a variety of unsaturated bonds with isopropanol in the absence of base additives.
- Long, Jilan,Zhou, Ying,Li, Yingwei
-
supporting information
p. 2331 - 2334
(2015/02/05)
-
- Diastereoselective and Enantioselective Silylation of 2-Arylcyclohexanols
-
The silylation-based kinetic resolution of trans 2-arylcyclohexanols was accomplished by employing a triaryl silyl chloride as the derivatizing reagent with a commercially available isothiourea catalyst. The methodology is selective for the trans diastereomer over the cis, which provides an opportunity to selectively derivatize one stereoisomer out of a mixture of four. By employing this technology, a facile, convenient method to form a highly enantiomerically enriched silylated alcohol was accomplished through a one-pot reduction-silylation sequence that started with a 2-aryl-substituted ketone.
- Wang, Li,Akhani, Ravish K.,Wiskur, Sheryl L.
-
supporting information
p. 2408 - 2411
(2015/05/27)
-
- Ruthenium Nanoparticles Stabilized in Cross-Linked Dendrimer Matrices: Hydrogenation of Phenols in Aqueous Media
-
Novel catalysts consisting of ruthenium nanoparticles encapsulated in cross-linked matrices based on the poly(propylene imine) dendrimers of the 1st and 3rd generations have been synthesized with a narrow particle size distribution (3.8 and 1.0 nm, respectively). The resulting materials showed high activity for the hydrogenation of phenols in aqueous media (specific catalytic activity reached turnover frequencies of 2975h-1 with respect to hydrogen uptake). It has been shown that the use of water as a solvent leads to a 1.5 to 50-fold increase in the reaction rate depending upon the nature of the substrate. It has been established that unlike the traditional heterogeneous catalysts based on ruthenium, during the hydrogenation of dihydroxybenzenes, the hydrogenation rate decreases in the order: resorcinol>hydroquinoneacatechol. The maximum specific activity for resorcinol was a turnover frequency of 243150h-1 with respect to hydrogen uptake. The catalyst based on the dendrimer of the 3rd generation containing finer particles has significantly inferior activity to the catalyst based on the dendrimer of the 1st generation by virtue of steric factors, as well as the need for prereduction of the ruthenium oxide contained on the surface. These catalysts showed resistance to metal leaching and may be reused several times without loss of activity.
- Maximov, Anton,Zolotukhina, Anna,Murzin, Vadim,Karakhanov, Edward,Rosenberg, Edward
-
p. 1197 - 1210
(2015/04/14)
-
- P-Tolylimido rhenium(v) complexes with phenolate-based ligands: Synthesis, X-ray studies and catalytic activity in oxidation with tert-butylhydroperoxide
-
The reactions of mer-[Re(p-NTol)X3(PPh3)2] (X = Cl, Br) with chelating phenolate-based ligands (2-(2-hydroxy-5-methylphenyl)benzotriazole (HL1), 2-(2-hydroxyphenyl)benzothiazole (HL2) or 2-(2-hydroxyphenyl)benzoxazole (HL3)) afforded a series of p-tolylimido rhenium(v) complexes cis- or trans-(X,X)-[Re(p-NTol)X2(L)(PPh3)]·yMeCN (where X = Cl, Br; L = L1, L2, L3 and y = 0-2) and [Re(p-NTol)X(L)(PPh3)2]Z·pPPh3 (where X = Cl, Br; Z = ReO4, PF6; L = L1, L2, L3 and p = 0 or 1). The reported compounds were characterized by elemental analysis, FT-IR, NMR (1H, 13C and 31P) and X-ray crystallography. Interestingly, the halide ions of [Re(p-NTol)Cl2(L1)(PPh3)]·MeCN (1) and [Re(p-NTol)Cl2(L2)(PPh3)]·2MeCN (3) are in cis relative dispositions, whereas the complexes [Re(p-NTol)Br2(L)(PPh3)] (L1 for 2, L2 for 4 and L3 for 6) and [Re(p-NTol)Cl2(L3)(PPh3)] (5) were found to be trans-(X,X) isomers. The compounds [Re(p-NTol)X(L)(PPh3)2](PF6) (X = Cl, Br; L = L1 and L2) and [Re(p-NTol)X(L3)(PPh3)2](PF6)·PPh3 (X = Cl, Br) have been tested in oxidative catalysis. A few compounds exhibited very good catalytic properties in oxidation of alcohols with tert-BuOOH (TBHP) in acetonitrile solution at moderate temperatures. Complex [Re(p-NTol)Cl(L2)(PPh3)2]PF6 (13) is the catalyst of choice for oxidation of 1-phenylethanol to acetophenone (in 80% yield; turnover number attained 290 after 30 h) and cyclooctanol to cyclooctanone (in 88% yield). Notably lower activity has been found in the oxidation of alkanes with TBHP. Product distribution in the oxidation of methylcyclohexane indicates some steric hindrance around the reaction center.
- Gryca, Izabela,Machura, Barbara,Malecki, Jan Grzegorz,Kusz, Joachim,Shul'Pina, Lidia S.,Ikonnikov, Nikolay S.,Shul'Pin, Georgiy B.
-
p. 334 - 351
(2015/12/26)
-