- Electrochemical hydrogenation of citral 1. The role of the copper cathode in the electroreduction of citral
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Alcohols (citronellol and isomeric nerol and geraniol) are the main products of the electroreduction of citral at the copper cathode in the presence in the AcOH in a water-DMF medium.It has been suggested that under the conditions of the electrolysis at the hydrogen reduction potential (E = -1.2 V) electroreduction of citral occurs according to the electrochemical hydrogenation mechanism.The total yield of the alcohols and the selectivity of the process depend on the preliminary treatment of the cathode.The electroreduction of citral at a mechanically cleaned cathode gives alcohols in 54percent total yield, and unsaturated alcohols are the prevailing products.Preliminary annealing of the cathode results in an increase in the total yield of alcohols in the electrolysis to 86percent and in the predominant formation of citronellol. - Key words: copper cathode, citral, citronellol, electrochemical hydrogenation, electroreduction, recrystallization.
- Korotyaeva, L. M.,Rubinskaya, T. Ya.,Gultyai, V. P.
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- Bis(phosphine)cobalt dialkyl complexes for directed catalytic alkene hydrogenation
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Planar, low-spin cobalt(II) dialkyl complexes bearing bidentate phosphine ligands, (P - P)Co-(CH2SiMe3)2, are active for the hydrogenation of geminal and 1,2-disubstituted alkenes. Hydrogenation of more hindered internal and endocyclic trisubstituted alkenes was achieved through hydroxyl group activation, an approach that also enables directed hydrogenations to yield contrasteric isomers of cyclic alkanes.
- Friedfeld, Max R.,Margulieux, Grant W.,Schaefer, Brian A.,Chirik, Paul J.
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- Chemoselective Hydrogenation of Aldehydes under Mild, Base-Free Conditions: Manganese Outperforms Rhenium
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Several hydride Mn(I) and Re(I) PNP pincer complexes were applied as catalysts for the homogeneous chemoselective hydrogenation of aldehydes. Among these, [Mn(PNP-iPr)(CO)2(H)] was found to be one of the most efficient base metal catalysts for this process and represents a rare example which permits the selective hydrogenation of aldehydes in the presence of ketones and other reducible functionalities, such as C=C double bonds, esters, or nitriles. The reaction proceeds at room temperature under base-free conditions with catalyst loadings between 0.1 and 0.05 mol% and a hydrogen pressure of 50 bar (reaching TONs of up to 2000). A mechanism which involves an outer-sphere hydride transfer and reversible PNP ligand deprotonation/protonation is proposed. Analogous isoelectronic and isostructural Re(I) complexes were only poorly active.
- Glatz, Mathias,St?ger, Berthold,Himmelbauer, Daniel,Veiros, Luis F.,Kirchner, Karl
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- Homogeneous electro-mediated reduction of unsaturated compounds using Ni and Fe as mediators in DMF
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The homogeneous electro-mediated reduction (HEMR) of several organic compounds (cyclohexene, cyclohexanone, acetophenone, benzaldehyde, styrene, linalool, 1,3-cyclohexadiene, citral, trans-4-phenyl-3-buten-2-one, and piperine) was carried out using Fe2+, Ni2+, and [NiII(bpy)]Br2 (bpy=2,2′-bipyridine) as electron mediators. An electrochemical system composed of sacrificial anode (Fe, Ni or Zn), nickel cathode, NaI (0.2 M) as supporting electrolyte in DMF and an undivided cell, was used. A constant current ≤100 mA was applied with a maximum cell potential of 2.0 V. Non-conjugated olefins are not reactive, but ketones may be easily reduced to the respective alcohol. In the case of conjugated olefins and ketones, [NiII(bpy)]Br2 or Ni2+ mediator presented good reactivity and selectivity in most cases. Fe2+ more efficiently mediates the reduction of carbonyl containing systems. Preliminary electroanalytical studies indicate the complexation of the organic substrate by Fe2+ and Ni2+ ions and [NiII(bpy)]Br2 complex.
- da Silva, Aderivaldo P.,Mota, Saulo D.C.,Bieber, Lothar W.,Navarro, Marcelo
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- Hydrogenation of alkenes with rhodium nanoparticles supported on SBA-15
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Rhodium nanoparticles were prepared by chemical reduction of RhCl 3·3H2O in presence of polyvinyl pyrrolidone and then immobilized on SBA-15 by impregnation. The catalyst was used for hydrogenation of unsaturated hydrocarbons at room temperature. The progress of the reaction was monitored by GC-MS and 100 % conversion was achieved in all cases.
- Bhorali, Nayanmoni,Ganguli, Jatindra Nath
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- Biphasic reduction of unsaturated aldehydes to unsaturated alcohols by ruthenium complex-catalyzed hydrogen transfer
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Unsaturated aldehydes can be reduced under very mild conditions (30-80 deg C) with good yields and excellent selcetivities to the corresponding unsaturated alcohols by hydrogen transfer from HCOONa/H2O catalyzed by a complex of RuII with sulphonated triphenylphosphine in aqueous/organic biphasic systems.
- Joo, Ferenc,Benyei, Attila
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- Reduction of carbonyl compounds by using polymethylhydrosiloxane: Reactivity and selectivity
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Reduction of aldehydes and ketones with PMHS [Me3SiO-(SiMe(H)O)(n)-SiMe3] proceeded smoothly in the presence of Bu4NF at -70°C or 0°C within 60 min in THF. High stereo- and chemoselectivities as well as functional group tolerance of this system are also presented.
- Kobayashi, Yuichi,Takahisa, Eisuke,Nakano, Miwa,Watatani, Kengo
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- Effect of 2-propanol on the transfer hydrogenation of aldehydes by aqueous sodium formate using a rhodium(i)-sulfonated triphenylphosphine catalyst
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In water/2-propanol mixtures [RhCl(mtppms)3] (mtppms = monosulfonated triphenylphosphine) was an efficient catalyst for the selective C=C reduction of trans-3-phenyl-2-propenal (trans-cinnamaldehyde) by hydrogen transfer from formate at temperatures as low as 30 °C. An outstandingly high catalyst turnover frequency of 1214 h-1 was determined at 70 °C. A possible mechanism of the reaction is suggested on the basis of kinetic studies and 1H- and 31P-NMR spectroscopic identification of the major Rh(i) species in the reaction mixtures as cis-mer-[H2RhX(mtppms)3] (X = HCOO- or H2O). It was established that a large part but not all of the rate increase observed in water/2-propanol mixtures in comparison with systems with neat water as solvent was the consequence of complete dissolution of trans-cinnamaldehyde on the effect of the co-solvent. Nevertheless, the rate showed a significant further increase with increasing 2-propanol concentration even in homogeneous solution and this was ascribed to changes in the solvent structure. The high catalyst activity in this solvent mixture allowed the transfer hydrogenation of citral. Although good to excellent conversions were observed at 30-70 °C, a useful degree of selectivity in hydrogenation of C=C vs. C=O bonds could not be achieved.
- Kathó, ágnes,Szatmári, Imre,Papp, Gábor,Joó, Ferenc
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- Hydrogenation of aldehydes and ketones to corresponding alcohols with methylamine borane in neat water
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GRAPHICAL ABSTRACT Chemoselective hydrogenation of various aldehydes and ketones with methylamine borane (MeAB) in neat water was investigated. MeAB is suitable for green organic reactions, for MeAB is a nontoxic, environmentally benign, and easily handled reagent. Aldehydes were selectively and rapidly hydrogenated in excellent yields (86-97%) for 30 min, but hydrogenation of aromatic ketones needed over 20 h at room temperature because of their poor water solubility and steric hindrance. Thus we investigated polyethylene glycol (PEG400) and acidic cation-exchange D072 resin as catalysts to accelerate the hydrogenation reaction of aromatic ketones and achieved excellent yields within several hours. PEG 400 and D072 resin are both suitable for green organic reactions. The D072 resin was reused up to four times without any significance loss in activity.
- Duan, Yifan,Bai, Ruijiao,Tian, Jun,Chen, Ligong,Yan, Xilong
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- Synthesis, crystal structure, and catalytic properties of MgCo 6Ge6
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The ternary compound MgCo6Ge6 represents a novel member of the RM6X6 phases, which contains a graphite-type Ge network, Kagome nets of Co atoms, and Ge2 dumbbells with an unexpected short Ge-Ge contact in the range of a localized Ge-Ge single bond. The title compound shows a large variety of chemical bonding, which ranges from metallic to multi-center and covalent bonding. The role of polar intermetallic alloys as promising candidates for the application as catalysts for the selective hydrogenation of α,β-unsaturated aldehydes is discussed. MgCo6Ge6 possesses a remarkable activity and selectivity for the hydrogenation of cis/trans-citral to geraniol and nerol.
- Gieck, Christine,Schreyer, Martin,Faessler, Thomas F.,Cavet, Sylwia,Claus, Peter
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- Selective liquid phase hydrogenation of citral on Au/Fe2O3 catalysts
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Gold supported on iron oxide hydrogenates citral (an α,β-unsaturated aldehyde) to the corresponding α,β-unsaturated alcohols (geraniol and nerol) with a selectivity higher than 95%.
- Milone,Tropeano,Gulino,Neri,Ingoglia,Galvagno
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- Liquid-phase citral hydrogenation over SiO2-supported Group VIII metals
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Citral hydrogenation was studied over SiO2-supported Group VIII metals at 300 K and 1 atm in the absence of all transport limitations as verified by the Madon-Boudart test and the Weisz-Prater criterion. The initial turnover frequency (TOF) for
- Singh, Utpal K.,Vannice, M. Albert
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- Selective transfer hydrogenation of carbonyl compounds by ruthenium nanoclusters supported on alkali-exchanged zeolite beta
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Selective transfer hydrogenation of aromatic ketones and β-keto esters to the corresponding alcohols was achieved by using ruthenium nanoclusters supported on alkali-exchanged zeolite beta catalyst. The high activity and selectivity of the catalyst is due to the presence of highly dispersed ruthenium clusters in combination with the large number of Bronsted acidic sites of zeolite.
- Kantam, M. Lakshmi,Rao, B. Purna Chandra,Choudary,Sreedhar
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- Hydrogenation of citral using monometallic Pt and bimetallic Pt-Ru catalysts on a mesoporous support in supercritical carbon dioxide medium
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Supercritical carbon dioxide was shown to be a suitable reaction medium for the highly efficient hydrogenation of citral using monometallic Pt and bimetallic Pt-Ru supported on a mesoporous material, MCM-48, as catalyst. A remarkable change in the product distribution was observed after the addition of Ru to the monometallic Pt catalyst in supercritical carbon dioxide. The monometallic Pt catalyst was found to be highly selective to the unsaturated alcohol (geraniol + nerol) at a temperature of 323 K within 2 h whereas the bimetallic catalyst becomes selective to the partially saturated aldehyde (citronellal) under the same reaction conditions. Phase behavior plays an important role in the product distribution. Highest conversion and high selectivity to citronellal were achieved in the homogeneous phase for the Pt-Ru catalyst while on the other hand the unsaturated alcohol (geraniol + nerol) was produced in the heterogeneous phase for the monometallic Pt catalyst. An XPS study offers strong evidence of the electronic modification of Pt after the addition of Ru in the bimetallic catalyst. The change in product distribution on the Pt-Ru bimetallic catalyst may be explained by the appreciable interaction between the medium and the metal particles promoted by the presence of metallic Ru.
- Chatterjee,Zhao,Ikushima
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- Design of catalyst systems for the one-pot synthesis of menthols from citral
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Stable, active, and highly selective bifunctional Ni/Al-MCM-41 catalysts were developed for the one-pot synthesis of menthols from citral. The liquid-phase hydrogenation of citral to citronellal was studied on silica-supported noble (Pt, Pd, Ir) and nonnoble (Ni, Co, Cu) metals. It was found that citronellal is selectively formed at the beginning of the reaction only on Pd and Ni catalysts. The consecutive ene-cyclization of citronellal to isopulegols was investigated on solid acids containing exclusively Lewis (ZnO/SiO2) or strong Broensted (CsHPA) acid sites, and also on catalysts containing both Lewis and Broensted acid sites of either strong (zeolites, SiO2-Al2O3) or moderate (Al-MCM-41) strength. The isopulegol formation rate was higher on samples exhibiting dual Lewis/Broensted acidity, such as SiO2-Al2O3, Al-MCM-41, and zeolite HBEA. Based on these previous results, bifunctional catalysts containing Pd or Ni supported on SiO2-Al2O3, Al-MCM-41, or zeolite HBEA were prepared and tested for citral conversion to menthols. The catalyst stability and the effect of hydrogen pressure and metal loading on menthol productivity were also investigated. The best catalyst was Ni(8%)/Al-MCM-41, which yielded more than 90% menthols at 2026.0 kPa and showed no significant deactivation after two consecutive catalytic tests.
- Trasarti,Marchi,Apesteguia
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- Biomass- And calcium carbide-based recyclable polymers
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Biomass is a renewable source of valuable feedstock for the chemical industry of the future. A promising approach to the utilization of valuable components of biomass is the synthesis of monomers and polymers, if the overall technology is designed for a clean cycle without pollution of the environment with newly created polymers. In this work, we have developed a methodology for the recycling of polymers based on biomass and calcium carbide. First, we modified a series of biomass-derived terpene alcohols with calcium carbide followed by polymerization of the isolated vinyl ethers. Then, to study the recycling potential, the obtained polymers were subjected to pyrolysis at moderate temperatures (200-450 °C). The pyrolysis products were analyzed using TGA-MS, GC-MS, and NMR, and it was found that the polymers can be transformed quite easily. The products of the pyrolysis consisted of the starting terpenols, as well as the corresponding non-toxic ketones or aldehydes: up to 87% of the starting alcohol or up to 100% of the total sum of alcohol + aldehyde or alcohol + ketone (GC-yields). Then, the reaction mixture was hydrogenated and resulted in the formation of starting alcohol only. According to the studied pathway of polymers re-building, a terpene fragment attached to the main polyethylene chain through an oxygen atom promotes the transformation of the obtained polymers. Thus, the products of pyrolysis are environmentally friendly and can be reused in the further synthesis of monomers. The developed system has shown a unique assembling/disassembling ability and advances the concept of reusable bio-derived high value-added materials.
- Metlyaeva, Svetlana A.,Rodygin, Konstantin S.,Lotsman, Kristina A.,Samoylenko, Dmitriy E.,Ananikov, Valentine P.
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- TRIBUTYLTIN HYDRIDE-INDUCED O-STANNYL KETYLS IN THE CYCLIZATION OF ALDEHYDES AND KETONES WITH ALKENES
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An aldehyde or a ketone connected by a tether to an olefin efficiently cyclizes in a free radical reaction mediated by tributyltin hydride.The effects of activated olefins on this reaction, which provides functionalized cyclopentane rings and γ-lactones from O-stannyl ketyls in a mild and regiocontrolled manner, were also studied.
- Enholm, Eric J.,Prasad, Girija
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- Chemoselective Pt-catalysts supported on carbon-TiO2 composites for the direct hydrogenation of citral to unsaturated alcohols
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A series of carbon xerogels-TiO2 composites with different TiO2 contents were prepared, exhaustively characterized and used as a Pt-support to develop selective hydrogenation catalysts. The carbon phase in the composite hinders the TiO2 crystal growth and the transformation to rutile during thermal treatments. Textural, chemical and catalytic properties are determined by the TiO2 content, with an optimum around 40 wt.% of TiO2 content. The mesoporosity of the supports, the Pt-dispersion and Pt-support interactions are favoured in this sense. During the H2-pretreatment, the Pt and TiO2 phases were simultaneously reduced and the formation of oxygen vacancies leads to the mobility of Pt-species inside the TiO2 structure, avoiding sintering in surface and strongly improving both catalytic activity and selectivity. The catalytic performance was discussed on the basis of the sample characteristics. Unsaturated alcohols were obtained as main reaction products in all cases, being the only product in the case of the optimized catalyst.
- Bailón-García, Esther,Carrasco-Marín, Francisco,Pérez-Cadenas, Agustín F.,Maldonado-Hódar, Francisco J.
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- A mild, efficient, inexpensive, and selective cleavage of primary tert-butyldimethylsilyl ethers by oxone in aqueous methanol
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(formula presented) The use of a 50% aqueous methonolic solution of Oxone is described for the selective cleavage of primary tert-butyldimethylsilyl and aryl ethers at room temperature. This method enables one to deprotect tert-butyldimethylsilyl ethers of primary alcohols in the presence of tertbutyldimethylsilyl ethers of secondary and tertiary alcohols and phenols. The silyl ethers of phenols were deprotected at longer reaction times.
- Sabitha, Gowravaram,Syamala, Mandali,Yadav
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- Transfer hydrogenation of carbonyl compounds catalyzed by ruthenium nanoparticles stabilized on nanocrystalline magnesium oxide by ionic liquids
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Transfer hydrogenation of various carbonyl compounds was achieved in excellent yields by ruthenium nanoparticles stabilized on the nanocrystalline magnesium oxide by the incorporation of choline hydroxide, a basic ionic liquid. The procedure is simple, efficient and the catalyst can be recycled five times.
- Lakshmi Kantam,Sudarshan Reddy,Pal, Ujjwal,Sreedhar,Bhargava
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- Selective Liquid-Phase Hydrogenation of Citral over Supported Palladium
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Citral in the liquid phase was reduced in a low-pressure hydrogenator by using catalysts consisting of palladium supported on (a) a mixed 80 : 20 SiO2/AlPO4 system and (b) sepiolite from Vallecas (Madrid, Spain). A kinetic study provided the reaction orders in the substrate concentration and hydrogen pressure. Experimental variables such as temperature, hydrogen pressure and the type of solvent were adjusted in order to optimize the reduction process. The presence of additives of the Lewis acid type such as FeCl2 was found to considerably alter the hydrogenation mechanism; under these conditions, the selectivity proved strongly dependent on the Fe2+/Pd atomic ratio. The reaction products were characterized by using gas chromatography in combination with mass spectrometry.
- Aramendia,Borau,Jimenez,Marinas,Porras,Urbano
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- Electrochemical hydrogenation of citral 4. * Role of the acid component in electrochemical hydrogenation
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The effect of the nature and concentration of the acid component on the yield and ratio of the products of electrocatalytic hydrogenation of citral was studied. The use of weak organic acids (e.g., AcOH) in amounts that are stoichiometric for hydrogenation of conjugated double bonds was shown to be advantageous.
- Korotayeva,Rubinskaya,Gultyai
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- Three asymmetric guanidinato metal complexes: Synthesis, crystal structures and their use as pre-catalysts in the Meerwein–Ponndorf–Verley reduction
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The guanidinatolithium compound [{(C2H5)2N}C(NC6H5)(NAr)LiOEt2]2(Ar = 2,6-Me2C6H3) (1), is readily accessible in high yield upon insertion reaction of lithium diethyl amide with unsymmetric carbodiimine [Formula presented]6H5. The reaction of 1 with AlCl3in Et2O afforded the guanidinatoaluminum compound [{(C2H5)2N}C(NC6H5)(NAr)]2AlCl (2). Compound 2 reacted with equivalent MeLi to give [{(C2H5)2N}C(NC6H5)(NAr)]2AlCH3(3), which was also prepared by the treatment of Et2NH with sequentially trimethylaluminum and carbodiimine [Formula presented]6H5in hexane. Compounds 1–3 were characterized by1H,13C NMR spectra and single crystal X-ray diffraction analysis. In addition, 1, 2 and 3 were used pre-catalyst to catalyze the Meerwein–Ponndorf–Verley reduction, and both of 2 and 3 exhibited good to excellent catalytic activity.
- Han, Hong-Fei,Zhang, Shao-Feng,Guo, Zhi-Qiang,Tong, Hong-Bo,Wei, Xue-Hong
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- Selective Hydrogenation of Citral on Pt-Containing Catalysts at Room Temperature and Atmospheric Pressure
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Abstract: It is shown that the 1% Pt/CeO2–ZrO2 (1% Pt/CZ) catalytic system allows selective hydrogenation of citral with a 94% conversion and a selectivity towards unsaturated alcohols of 59% at room temperature and atmospheric pressure. The effect of addition of alkali to the reaction mixture on the yield of the target products is studied, and the optimum conditions of the reaction are determined.
- Vikanova,Redina
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- Supported Co–Re Bimetallic Catalysts with Different Structures as Efficient Catalysts for Hydrogenation of Citral
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Bimetallic Co–Re/TiO2 catalysts were developed for efficient citral hydrogenation. Bimetallic catalysts were prepared by co-impregnation (CI), successive-impregnation (SI), and surface redox method (SR). The arrangement between the Co and Re species on these systems was fully characterized using several techniques (TEM–energy-dispersive X-ray spectroscopy, H2 temperature-programmed reduction, temperature-programmed desorption, XRD, CO FTIR spectroscopy, model reaction of cyclohexane dehydrogenation), and their catalytic performances were evaluated for the selective hydrogenation of citral towards unsaturated alcohols. The Re and Co species are completely isolated in the CI sample, presenting a very limited Co–Re interaction. In SI samples, the metals coexist in a Janus-type structure with a concentration of Re around Co. Decoration/core–shell structures are observed for SR samples resulting from the redox exchange between the metallic surface of the parent Co/TiO2 catalyst and the Re7+ species of the modifier precursor salt. The contact degree between the two metals gradually increases as follows: Isolated structure (CI)a disadvantage for the hydrogenation reaction. For SR samples, the increase of Re loading contributes to the electron transfer from Re to Co that is consistent with a change of structure from decoration to core–shell. The lack of directly accessible Co atoms for SR catalysts with fully coated structure decreases the efficiency of Re reduction. The presence of Co–Re interaction resulting from the close contact between metals plays a dominant role in the hydrogenation of citral. Nevertheless, an excessively high contact degree is unnecessary for citral hydrogenation once Co–Re interaction has formed.
- Di, Xin,Lafaye, Gwendoline,Especel, Catherine,Epron, Florence,Qi, Ji,Li, Chuang,Liang, Changhai
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- Electrochemical hydrogenation of citral 2. The effect of the components of the medium on the process of electrochemical reduction at a copper cathode
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The factors (concentration of citral, composition of the solvent, AcOH : citral ratio) affecting electrochemical hydrogenation of citral at an annealed copper cathode have been determined.The highest total yield (94percent) of the alcohols (nerol, geraniol, citranellol) with a considerable predominance of the latter is achieved at 40percent DMF in water, citral concentration 0.02 M, and AcOH : citral ratio = 10 : 1.The transition to purely organic or purely aqueous media leads to a decrease in both the total yield of the alcohols and the selectivity of the process. - Key words: copper cathode, citral, citronellol, electrochemical hydrogenation.
- Rubinskaya, T. Ya.,Korotayeva, L. M.,Gul'tyai, V. P.
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- Manufacture of Citronellal by the Rhodium-Catalyzed Homogeneous Hydrogenation of Neral
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The highly chemoselective hydrogenation of neral affording citronellal is described. The reaction has been conducted with homogeneous rhodium complexes. Among the set of ancillary diphosphane ligands tested, Xantphos was found to be superior. The relevant precatalyst has been generated from neutral metal sources such as Rh(acac)(CO)2 or the carbon monoxide-free rhodium source Rh(acac)(cod) in the absence of any base. A high activity and chemoselectivity in favor of the desired citronellal is achieved at 0.1 MPa and room temperature. Under the same conditions, geranial is also reduced to citronellal. The addition of carbon monoxide to the hydrogen stream as used in an industrial process is not necessary. (Figure presented.).
- Holz, Jens,Doerfelt, Stephan,B?rner, Armin
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- Highly Efficient and Selective Hydrogenation of Aldehydes: A Well-Defined Fe(II) Catalyst Exhibits Noble-Metal Activity
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The synthesis and application of [Fe(PNPMe-iPr)(CO)(H)(Br)] and [Fe(PNPMe-iPr)(H)2(CO)] as catalysts for the homogeneous hydrogenation of aldehydes is described. These systems were found to be among the most efficient catalysts for this process reported to date and constitute rare examples of a catalytic process which allows selective reduction of aldehydes in the presence of ketones and other reducible functionalities. In some cases, TONs and TOFs of up to 80000 and 20000 h-1, respectively, were reached. On the basis of stoichiometric experiments and computational studies, a mechanism which proceeds via a trans-dihydride intermediate is proposed. The structure of the hydride complexes was also confirmed by X-ray crystallography.
- Gorgas, Nikolaus,St?ger, Berthold,Veiros, Luis F.,Kirchner, Karl
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- Surface Lewis acid-promoted copper-based nanocatalysts for highly efficient and chemoselective hydrogenation of citral to unsaturated allylic alcohols
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Chemoselective hydrogenation of α,β-unsaturated aldehydes or ketones to unsaturated alcohols (UAs) is one of the key processes for the production of various important intermediate chemicals. In the present work, well-dispersed ZnO-promoted supported copper nanocatalysts were generated from Cu-Zn-Al layered double hydroxide (CuZnAl-LDH) precursors for liquid-phase chemoselective hydrogenation of citral to allylic alcohols (geraniol and nerol isomers). A series of characterizations including XRD, TEM, STEM, XPS, H2-TPR, and Py-IR demonstrated that the microstructure and catalytic performance of as-formed Cu-based nanocatalysts were significantly affected by the incorporation of Zn into catalyst precursors. It was found that the addition of more ZnO to catalysts could result in better metal dispersion and an increase in the surface Cu+/(Cu+ + Cu0) ratio and surface Lewis acid sites. In liquid-phase chemoselective hydrogenation of citral, a high selectivity toward allylic alcohols (>75%) at complete citral conversion was achieved successfully on as-formed non-noble-metal Cu-based nanocatalysts with a Cu/Zn molar ratio of 2:1 under mild reaction conditions (e.g. 80°C, 1.0 MPa). The high efficiency of the catalysts was attributed mainly to both the synergism between Cu0 and Cu+ species and the promotion of surface Lewis acid sites, thereby improving the dissociation of hydrogen and facilitating the adsorption of the citral molecule and the following activation of the carbonyl group during the citral hydrogenation.
- Li, Wei,Fan, Guoli,Yang, Lan,Li, Feng
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- An efficient reduction system - NiCl2·6H2O-Zn/DMF-H2O for conversion of aldehydes to alcohols
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Aldehydes were efficiently converted to the corresponding alcohols at room temperature, with NiCl2·6H2O-Zn/DMF-H2O system.
- Baruah, Robindra N.
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- Electrochemical hydrogenation of citral 5. * The use of a nickel electrode in the electrocatalytic process
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The conditions for preparative electrocatalytic hydrogenation of citral to citronellol were found. Changes in the electrocatalytic properties of the nickel cathode depend on the method of pretreatment of the electrode (mechanical surface cleaning, thermal treatment, cathode-anode activation, and electrodeposition). The use of the nickel cathode with the surface covered with dispersed nickel in electrocatalytic hydrogenation was recommended.
- Korotayeva,Rubinskaya,Gultyai
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- Tuning selectivity in terpene chemistry: Selective hydrogenation versus cascade reactions over copper catalysts
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The selectivity of Cu/Al2O3 under very mild catalytic hydrogenation conditions can be tuned only by switching the solvent. Geraniol can be converted in a one-pot one-step process into a mixture of citronellol and menthol in hydrocarbon solvents or reduced to citronellol with 98% selectivity in 2-propanol without any additive. Both reactions can be applied to essential oils or synthetic mixtures containing geraniol, citronellal and nerol.
- Zaccheria,Ravasio,Fusi,Rodondi,Psaro
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- Purification and characterization of an α-L-rhamnosidase from Pichia angusta X349
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An intracellular α-L-rhamnosidase from Pichia angusta X349 was purified to homogeneity through four chromatographic steps. The α-L-rhamnosidase appeared to be a monomeric protein with a molecular mass of 90 kDa. The enzyme had an isoelectric point at 4.9, and was optimally active at pH 6.0 and at around 40°C. The Ki for L-rhamnose inhibition was 25 mM. The enzyme was inhibited by Cu2+, Hg2+, and p-chloromercuribenzoate. The α-L-rhamnosidase was highly specific for α-L-rhamnopyranoside and liberated rhamnose from naringin, rutin, hesperidin, and 3-quercitrin. The α-L-rhamnosidase was active at the ethanol concentrations of wine. It efficiently released monoterpenols, such as linalool and geraniol, from an aroma precursor extracted from Muscat grape juice.
- Yanai, Takaaki,Sato, Michikatsu
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- Magnetic nickel ferrite nanoparticles as highly durable catalysts for catalytic transfer hydrogenation of bio-based aldehydes
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Magnetic nickel ferrite (NiFe2O4) nanoparticles were exploited as stable and easily separable heterogeneous catalysts for catalytic transfer hydrogenation (CTH) of furfural to furfuryl alcohol with 2-propanol as both the hydrogen source and the solvent providing 94% product yield at 180 °C after 6 h of reaction. The magnetic properties of the catalysts provided facile recovery using an external magnet after reaction allowing it to be reused in five reaction cycles without loss of catalytic performance. Importantly, the NiFe2O4 nanoparticles were also applicable to CTH of other alkenyl/allyl/aromatic aldehydes affording over 94% selectivity towards the targeted alcohol products, thus being attractive as highly universal catalysts for CTH of aldehydes.
- He, Jian,Yang, Song,Riisager, Anders
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- Chemoselective Transfer Hydrogenation of Aldehydes with HCOONH4 Catalyzed by RuCl(CNNPh)(PP) Pincer Complexes
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Aldehydes were chemoselectively reduced to primary alcohols by using HCOONH4 as the hydrogen donor through transfer hydrogenation catalyzed by benzo[h]quinoline pincer complexes RuCl(CNNPh)(PP) at substrate to catalyst molar ratios of 2000 to 20 000. This practical reaction performed with aldehydes of commercial-grade purity in a water/toluene biphasic system afforded alcohols without the formation of condensation or amination side products.
- Baldino, Salvatore,Facchetti, Sarah,Nedden, Hans Günter,Zanotti-Gerosa, Antonio,Baratta, Walter
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- Direct synthesis of hybrid layered double hydroxide-carbon composites supported Pd nanocatalysts efficient in selective hydrogenation of citral
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This present study reports a facile one-pot strategy for the direct synthesis of hybrid layered double hydroxide (LDH)-carbon composites supported palladium nanocatalysts by the in situ reduction of PdCl42--intercalated MgAl-LDH combined with amorphous carbon under mild hydrothermal conditions. The results demonstrated that most of the Pd(II) species intercalated in the interlameller space of MgAl-LDH could be reduced in situ to metallic Pd0 species, and simultaneously, the hybrid structure of the LDH-C composites facilitated the formation of uniform Pd nanoparticles with small diameter, as well as the strong metal-support interactions. Furthermore, with the decreasing proportion of the LDH component in LDH-C composites, the average diameter of Pd nanoparticles decreased progressively and the metal-support interactions were weakened. The as-formed supported Pd nanocatalyst with Pd loading of 5.5 wt% was found to show a superior catalytic activity in the liquid-phase selective hydrogenation of citral than other supported Pd nanocatalysts, while the one with the Pd loading of 2.7 wt% yielded a much higher yield of citronellal (～80.0%) at 100% conversion. The catalytic performance of Pd nanocatalysts was proposed to be mainly related to both the metal-support interactions and the compositions of hybrid LDH-C composite supports.
- Han, Ruirui,Nan, Chunshi,Yang, Lan,Fan, Guoli,Li, Feng
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- Highly efficient Meerwein-Ponndorf-Verley reductions over a robust zirconium-organoboronic acid hybrid
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The Meerwein-Ponndorf-Verley (MPV) reaction is an attractive approach to selectively reduce carbonyl groups, and the design of advanced catalysts is the key for these kinds of interesting reactions. Herein, we fabricated a novel zirconium organoborate using 1,4-benzenediboronic acid (BDB) as the precursor for MPV reduction. The prepared Zr-BDB had excellent catalytic performance for the MPV reduction of various biomass-derived carbonyl compounds (i.e., levulinate esters, aldehydes and ketones). More importantly, the number of borate groups on the ligands significantly affected the catalytic activity of the Zr-organic ligand hybrids, owing to the activation role of borate groups on hydroxyl groups in the hydrogen source. Detailed investigations revealed that the excellent performance of Zr-BDB was contributed by the synergetic effect of Zr4+and borate. Notably, this is the first work to enhance the activity of Zr-based catalysts in MPV reactions using borate groups.
- Song, Jinliang,Hua, Manli,Huang, Xin,Visa, Aurelia,Wu, Tianbin,Fan, Honglei,Hou, Minqiang,Zhang, Zhaofu,Han, Buxing
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- Triphenylphosphine Dibromide: Effective and Selective Reagent for the Cleavage of Acetals
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Triphenylphosphine dibromide (PPh3Br2) is a mild and highly effective reagent for hydrolysis of various acetals in dichloromethane at low temperature.
- Wagner, Alain,Heitz, Marie-Paule,Mioskowski, Charles
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- Electrochemical hydrogenation of citral: 3. Effect of the nature of the solvent on electrocatalytic hydrogenation at a copper cathode
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The effect of a water-organic mixed solvent of varying composition (H2O-DMF, H2O-EtOH) on the selectivity of electrocatalytic hydrogenation of citral at a copper cathode was studied. The experimental results were discussed from the standpoint of the effect of the solvent structure on the heterogeneous electrochemical process involving a bulky organic molecule.
- Rubinskaya,Korotaeva,Gultyai
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- Hydrogenation of citral on activated carbon and high-surface-area graphite-supported ruthenium catalysts modified with iron
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The hydrogenation of citral has been performed over Ru-Fe catalysts supported on activated carbon and on high-surface-area graphite. It was found that selectivity to unsaturated alcohols is independent of the carbonaceous support used for ruthenium catalysts. The addition of iron enhances selectivity to unsaturated alcohols (geraniol and nerol) in a manner similar for both ruthenium catalysts, becoming maximum for the highest iron loading. Calorimetric experiments give some evidence about alloy formation in ruthenium catalysts promoted with iron. It is inferred that the surface polarity of the alloyed particles promotes the selective hydrogenation of citral toward unsaturated alcohols.
- Bachiller-Baeza,Guerrero-Ruiz,Wang,Rodriguez-Ramos
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- SELECTIVE REDUCTION OF ALDEHYDES
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Tetraethylammonium borohydride performs the selective reduction of aldehydes under mild conditions.
- Sorrell, Thomas N.,Pearlman, Paul S.
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- Chemoselective Supported Ionic-Liquid-Phase (SILP) Aldehyde Hydrogenation Catalyzed by an Fe(II) PNP Pincer Complex
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A base-tolerant supported ionic-liquid-phase (SILP) system containing a well-defined hydride Fe(II) PNP pincer complex has been prepared, structurally characterized, and used as catalyst in the hydrogenation of aldehydes to alcohols. The new SILP catalyst, with the optimum pore filling, was highly active exhibiting TONs and TOFs of up to 1000 and 4000 h-1, respectively, under mild conditions (25 °C, 10-50 bar H2 pressure) without significant leaching of both the complex and the IL.
- Brünig, Julian,Csendes, Zita,Weber, Stefan,Gorgas, Nikolaus,Bittner, Roland W.,Limbeck, Andreas,Bica, Katharina,Hoffmann, Helmuth,Kirchner, Karl
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- On-the-fly Catalyst Accretion and Screening in Chemoselective Flow Hydrogenation
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Herein, it is reported an on-the-fly accretion/reaction protocol to evaluate the structure-performance relationship in the chemoselective flow citral hydrogenation over Ni-based catalysts. Based on the methodology one was able to determine Ni nanoparticles ideal average size (ca. 9 nm), in a rapid and facile manner. The methodology offers a simple workflow, cost-effective and adaptable strategy for process intensification and optimization.
- Giziński, Damian,B?achucki, Wojciech,?r?bowata, Anna,Zienkiewicz-Machnik, Ma?gorzata,Goszewska, Ilona,Matus, Krzysztof,Lisovytskiy, Dmytro,Pisarek, Marcin,Szlachetko, Jakub,Sá, Jacinto
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- Continuous synthesis of menthol from citronellal and citral over Ni-beta-zeolite-sepiolite composite catalyst
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One-pot continuous synthesis of menthols both from citronellal and citral was investigated over 5 wt% Ni supported on H-Beta-38-sepiolite composite catalyst at 60–70 °C under 10–29 bar hydrogen pressure. A relatively high menthols yield of 53% and 49% and stereoselectivity to menthol of 71–76% and 72–74% were obtained from citronellal and citral respectively at the contact time 4.2 min, 70 °C and 20 bar. Citral conversion noticeably decreased with time-on-stream under 10 and 15 bar of hydrogen pressure accompanied by accumulation of citronellal, the primary hydrogenation product of citral, practically not affecting selectivity to menthol. A substantial amount of defuctionalization products observed during citral conversion, especially at the beginning of the reaction (ca. 1 h), indicated that all intermediates could contribute to formation of menthanes. Ni/H-Beta-38-sepiolite composite material prepared by extrusion was characterized by TEM, SEM, XPS, XRD, ICP-OES, N2 physisorption and FTIR techniques to perceive the interrelation between the physico-chemical and catalytic properties.
- Er?nen, Kari,M?ki-Arvela, P?ivi,Martinez-Klimov, Mark,Muller, Joseph,Murzin, Dmitry Yu.,Peurla, Markus,Simakova, Irina,Vajglova, Zuzana
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- A facile and versatile electro-reductive system for hydrodefunctionalization under ambient conditions
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A general electrochemical system for reductive hydrodefunctionalization is described, employing the inexpensive and easily available triethylamine (Et3N) as a sacrificial reductant. This protocol is characterized by facile operation, sustainable conditions, and exceptionally wide substrate scope covering the cleavage of C-halogen, N-S, N-C, O-S, O-C, C-C and C-N bonds. Notably, the selectivity and capability of reduction can be conveniently switched by simple incorporation or removal of an alcohol as a co-solvent.
- Huang, Binbin,Guo, Lin,Xia, Wujiong
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supporting information
p. 2095 - 2103
(2021/03/26)
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- Iron-catalyzed chemoselective hydride transfer reactions
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A Diaminocyclopentadienone iron tricarbonyl complex has been applied in chemoselective hydrogen transfer reductions. This bifunctional iron complex demonstrated a broad applicability in mild conditions in various reactions, such as reduction of aldehydes over ketones, reductive alkylation of various functionalized amines with functionalized aldehydes and reduction of α,β-unsaturated ketones into the corresponding saturated ketones. A broad range of functionalized substrates has been isolated in excellent yields with this practical procedure.
- Coufourier, Sébastien,Ndiaye, Daouda,Gaillard, Quentin Gaignard,Bettoni, Léo,Joly, Nicolas,Mbaye, Mbaye Diagne,Poater, Albert,Gaillard, Sylvain,Renaud, Jean-Luc
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supporting information
(2021/06/07)
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- Deep eutectic solvents as H2-sources for Ru(II)-catalyzed transfer hydrogenation of carbonyl compounds under mild conditions
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The employment of easily affordable ruthenium(II)-complexes as pre-catalysts in the transfer hydrogenation of carbonyl compounds in deep eutectic media is described for the first time. The eutectic mixture tetrabutylammonium bromide/formic acid = 1/1 (TBABr/HCOOH = 1/1) acts both as reaction medium and hydrogen source. The addition of a base is required for the process to occur. An extensive optimization of the reaction conditions has been carried out, in terms of catalyst loading, type of complexes, H2-donors, reaction temperature and time. The combination of the dimeric complex [RuCl(p-cymene)-μ-Cl]2 (0.01–0.05 eq.) and the ligand dppf (1,1′-ferrocenediyl-bis(diphenylphosphine)ferrocene) in 1/1 molar ratio has proven to be a suitable catalytic system for the reduction of several and diverse aldehydes and ketones to their corresponding alcohols under mild conditions (40–60 °C) in air, showing from moderate to excellent tolerability towards different functional groups (halogen, cyano, nitro, phenol). The reduction of imine compounds to their corresponding amine derivatives was also studied. In addition, the comparison between the results obtained in TBABr/HCOOH and in organic solvents suggests a non-innocent effect of the DES medium during the process.
- Cavallo, Marzia,Arnodo, Davide,Mannu, Alberto,Blangetti, Marco,Prandi, Cristina,Baratta, Walter,Baldino, Salvatore
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supporting information
(2021/02/22)
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- Selective, base-free hydrogenation of aldehydes catalyzed by IR complexes based on proton-responsive lutidine-derived CNP ligands
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Metal catalysts based on ligands containing proton-responsive sites have found widespread applications in the hydrogenation of polar unsaturated substrates. In this contribution, Ir complexes incorporating lutidine-derived CNP (C = N-heterocyclic carbene, NHC; P = phosphine) pincer ligands with two nonequivalent Br?nsted acid/base sites have been examined in the hydrogenation of aldehydes. To this end, Ir(CNP)H2Cl complexes were synthesized in two steps from the CNP ligand precursors and Ir(acac)(COD). These derivatives react with an excess of NaH to yield the trihydride derivatives Ir(CNP)H3, which were assessed as catalyst precursors in the hydrogenation of a series of aldehydes. The catalytic reactions were performed using commercial-grade substrates under neutral, mild conditions (0.1 mol % Ir-CNP; 4 bar H2, room temperature) with high conversions and selectivities for the reduction of the carbonyl function in the presence of other readily reducible groups such as C=C, nitro, and halogens. Reaction of an Ir(CNP)H2Cl complex with base in the presence of an aromatic aldehyde produces the reversible formation of alkoxide Ir complexes in which the aldehyde is bound to the deprotonated pincer framework (CNP*) through the CH-NHC arm of the ligand. These species, along with a carboxylate complex resulting from the Ir mediated oxidation of the aldehyde by water, is observed in the reaction of Ir(CNP)H3 with benzaldehyde. Finally, investigation of the mechanism of the hydrogenation of aldehydes has been carried out by means of DFT calculations considering the involvement of each arm of the Ir-CNP/CNP* derivatives. Calculations support a mechanism in which the catalyst switches its metal?ligand cooperation sites to follow the lowest energy pathway for each step of the catalytic cycle.
- álvarez, Eleuterio,Hernández-Juárez, Martín,López-Serrano, Joaquín,Paneque, Margarita,Rendón, Nuria,Sánchez, Práxedes,Suárez, Andrés
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p. 1314 - 1327
(2021/05/31)
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- Highly Selective Hydrogenation of C═C Bonds Catalyzed by a Rhodium Hydride
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Under mild conditions (room temperature, 80 psi of H2) Cp*Rh(2-(2-pyridyl)phenyl)H catalyzes the selective hydrogenation of the C═C bond in α,β-unsaturated carbonyl compounds, including natural product precursors with bulky substituents in the β position and substrates possessing an array of additional functional groups. It also catalyzes the hydrogenation of many isolated double bonds. Mechanistic studies reveal that no radical intermediates are involved, and the catalyst appears to be homogeneous, thereby affording important complementarity to existing protocols for similar hydrogenation processes.
- Gu, Yiting,Lisnyak, Vladislav G.,Norton, Jack R.,Salahi, Farbod,Snyder, Scott A.,Zhou, Zhiyao
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supporting information
p. 9657 - 9663
(2021/07/19)
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- Nickel-Catalyzed Formal Aminocarbonylation of Unactivated Alkyl Iodides with Isocyanides
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Herein, we disclose a Ni-catalyzed formal aminocarbonylation of primary and secondary unactivated aliphatic iodides with isocyanides to afford alkyl amide, which proceeds via the selective monomigratory insertion of isocyanides with alkyl iodides, subsequent β-hydride elimination, and hydrolysis process. The reaction features wide functional group tolerance under mild conditions. Additionally, the selective, one-pot hydrolysis of reaction mixture under acid conditions allows for expedient synthesis of the corresponding alkyl carboxylic acid.
- Chen, Yifeng,Huang, Wenyi,Qu, Jingping,Shrestha, Mohini,Wang, Yun,Weng, Yangyang
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supporting information
p. 3245 - 3250
(2020/04/21)
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- Cyclopentadienone iron tricarbonyl complexes-catalyzed hydrogen transfer in water
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The development of efficient and low-cost catalytic systems is important for the replacement of robust noble metal complexes. The synthesis and application of a stable, phosphine-free, water-soluble cyclopentadienone iron tricarbonyl complex in the reduction of polarized double bonds in pure water is reported. In the presence of cationic bifunctional iron complexes, a variety of alcohols and amines were prepared in good yields under mild reaction conditions.
- Coufourier, Sébastien,Gaillard, Sylvain,Mbaye, Mbaye Diagne,Ndiaye, Daouda,Renaud, Jean-Luc
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supporting information
(2020/01/28)
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- Chemoenzymatic Synthesis of 5-Hydroxymethylfurfural (HMF)-Derived Plasticizers by Coupling HMF Reduction with Enzymatic Esterification
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Biobased plasticizers, as substitutes for phthalates, have been synthesized from 5-hydroxymethylfurfural (HMF) and carboxylic acids (or esters) through a chemoenzymatic cascade process that involves as its first step the reduction of 5-hydroxymethylfurfural into 2,5-bis(hydroxymethyl)furan (BHMF), followed by the esterification of BHMF with carboxylic acids (or esters) by using a supported lipase (Novozym 435). The reduction of HMF into BHMF is performed by using monodisperse metallic Co nanoparticles with a thin carbon shell (Co@C) with high activity and selectivity. After optimization of reaction conditions (temperature, hydrogen pressure, and solvent), it is possible to achieve 97 % conversion of HMF with 99 % selectivity to BHMF after 2 h reaction time. The reduction of HMF and esterification of BHMF using carboxylic acids or vinyl esters as acyl donors by lipase are optimized separately in batch and in fixed-bed continuous reactors. The coupling of two flow reactors (for reduction and subsequent esterification) working under optimized reaction conditions affords the diesters of BHMF in roughly 90 % yield with no loss of activity during 60 h of operation.
- Arias, Karen S.,Carceller, Jose M.,Climent, Maria J.,Corma, Avelino,Iborra, Sara
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p. 1864 - 1875
(2020/03/11)
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- Catalytic Hydrogenation of Thioesters, Thiocarbamates, and Thioamides
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Direct hydrogenation of thioesters with H2 provides a facile and waste-free method to access alcohols and thiols. However, no report of this reaction is documented, possibly because of the incompatibility of the generated thiol with typical hydrogenation catalysts. Here, we report an efficient and selective hydrogenation of thioesters. The reaction is catalyzed by an acridine-based ruthenium complex without additives. Various thioesters were fully hydrogenated to the corresponding alcohols and thiols with excellent tolerance for amide, ester, and carboxylic acid groups. Thiocarbamates and thioamides also undergo hydrogenation under similar conditions, substantially extending the application of hydrogenation of organosulfur compounds.
- Luo, Jie,Rauch, Michael,Avram, Liat,Ben-David, Yehoshoa,Milstein, David
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supporting information
p. 21628 - 21633
(2021/01/11)
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- Continuous flow synthesis of menthol: Via tandem cyclisation-hydrogenation of citronellal catalysed by scrap catalytic converters
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A continuous flow synthesis of menthol starting from citronellal catalysed by scrap catalytic converters is reported. The reaction was conducted in a tandem system connecting in series two catalytic systems, with the first having Lewis acid properties (favouring the cyclisation of citronellal to isopulegols) and the second having hydrogenation catalytic activity (catalysing the hydrogenation of isopulegols to menthols). A Lewis acid catalyst was prepared by supporting iron oxide nanoparticles over a waste material, i.e. the ceramic core of scrap catalytic converters (SCATs) via a microwave assisted method. Most importantly, SCATs, containing a low residual noble metal content, could be directly employed in the second step as hydrogenation catalysts. The reaction was performed studying the influence on the yield and selectivity to (-)-menthol of various reaction parameters (T, p and flow rate). Under the best reaction conditions (at a flow rate of 0.1 mL min-1 and at 373 K and 413 K for cyclisation and hydrogenation steps respectively) a conversion of >99% of (+)-citronellal to (-)-menthol with 77% final yield was achieved.
- Zuliani, Alessio,Cova, Camilla Maria,Manno, Roberta,Sebastian, Victor,Romero, Antonio A.,Luque, Rafael
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p. 379 - 387
(2020/02/13)
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- Improved method for preparation of nerol and geraniol and catalytic system thereof
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The invention relates to a method for preparing nerol and geraniol through selective hydrogenation by taking citral as a raw material and a catalytic system for the method. The method comprises the following step: carrying out selective hydrogenation reaction on initial compound citral under the catalytic action of a homogeneous catalyst and an auxiliary agent to prepare nerol and geraniol. According to the method and the catalytic system provided by the invention, by-products citronellol and nerol isomers I-III in the reaction process are remarkably reduced, and the method has a relatively good industrial prospect.
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Paragraph 0054-0055; 0058-0059
(2020/05/01)
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- Novel nickel nanoparticles stabilized by imidazolium-amidinate ligands for selective hydrogenation of alkynes
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The main challenge in the hydrogenation of alkynes into (E)- or (Z)-alkenes is to control the selective formation of the alkene, avoiding the over-reduction to the corresponding alkane. In addition, the preparation of recoverable and reusable catalysts is of high interest. In this work, we report novel nickel nanoparticles (Ni NPs) stabilized by three different imidazolium-amidinate ligands (ICy·(Ar)NCN; L1: Ar = p-tol, L2: Ar = p-anisyl and L3: Ar = p-ClC6H4). The as-prepared Ni NPs were fully characterized by (HR)-TEM, XRD, WASX, XPS and VSM. The nanocatalysts are active in the hydrogenation of various substrates. They present a remarkable selectivity in the hydrogenation of alkynes towards (Z)-alkenes, particularly in the hydrogenation of 3-hexyne into (Z)-3-hexene under mild reaction conditions (room temperature, 3% mol Ni and 1 bar H2). The catalytic behaviour of Ni NPs was influenced by the electron donor/acceptor groups (-Me, -OMe, -Cl) in the N-aryl substituents of the amidinate moiety of the ligands. Due to the magnetic character of the Ni NPs, recycling experiments were successfully performed after decantation in the presence of an external magnet, which allowed us to recover and reuse these catalysts at least 3 times preserving both activity and chemoselectivity.
- López-Vinasco, Angela M.,Martínez-Prieto, Luis M.,Asensio, Juan M.,Lecante, Pierre,Chaudret, Bruno,Cámpora, Juan,Van Leeuwen, Piet W. N. M.
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p. 342 - 350
(2020/02/04)
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- Simple H2-free hydrogenation of unsaturated monoterpenoids catalyzed by Raney nickel
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A series of monoterpenoids (citral, carvone, menthone, camphor) as well as cyclohexanone and hex-5-en-2-one were subjected to transfer hydrogenation with PriOH/Raney nickel system at 82 or 150 °C. Among monoterpenoids, citral and carvone underwent full conversion at 82 °C within 5 h.
- Philippov, Alexey A.,Chibiryaev, Andrey M.,Martyanov, Oleg N.
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p. 380 - 381
(2019/08/20)
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- Selective Deprotection of the Diphenylmethylsilyl (DPMS) Hydroxyl Protecting Group under Environmentally Responsible, Aqueous Conditions
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Two new methods for selective deprotection of diphenylmethylsilyl (DPMS) ethers are described. Unmasking can be achieved with either catalytic amounts of perfluoro-1-butanesulfonyl fluoride (a SuFEx reagent) under mild, aqueous micellar conditions, or using stoichiometric amounts of 18-crown-6 ether in aqueous ethanol.
- Akporji, Nnamdi,Lieberman, Josh,Maser, Michael,Yoshimura, Masahiko,Boskovic, Zarko,Lipshutz, Bruce H.
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p. 5743 - 5747
(2019/11/11)
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- HYDROGENATION OF CARBONYLS WITH TETRADENTATE PNNP LIGAND RUTHENIUM COMPLEXES
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The present invention relates to catalytic hydrogenation processes, using Ru complexes with tetradentate ligands of formula L in hydrogenation processes for the reduction of ketone, aldehyde, ester or lactone into the corresponding alcohol or diol respectively. The described processes use a ruthenium complex of the formula (1) as defined below, and where the ligand (L) is defined by the Markush formula shown above.
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Page/Page column 27; 35
(2019/10/04)
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- Diaminodiphosphine tetradentate ligand and ruthenium complex thereof, and preparation methods and applications of ligand and complex
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The invention discloses a diaminodiphosphine tetradentate ligand and a ruthenium complex thereof, and preparation methods and applications of the ligand and the complex, and provides a ruthenium complex represented by a formula I, wherein L is a diaminodiphosphine tetradentate ligand represented by a formula II, and X and Y are respectively and independently chlorine ion, bromine ion, iodine ion,hydrogen negative ion or BH4. According to the present invention, the ruthenium complex exhibits excellent catalytic activity in the catalytic hydrogenation reactions of ester compounds, has high yield and high chemical selectivity, is compatible with conjugated and non-conjugated carbon-carbon double bond, carbon-carbon triple bond, epoxy, halogen, carbonyl and other functional groups, and hasgreat application prospects.
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Paragraph 0307-0309; 0311
(2019/11/04)
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- Aminoxyl-Catalyzed Electrochemical Diazidation of Alkenes Mediated by a Metastable Charge-Transfer Complex
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We report the development of a new aminoxyl radical catalyst, CHAMPO, for the electrochemical diazidation of alkenes. Mediated by an anodically generated charge-transfer complex in the form of CHAMPO-N3, radical diazidation was achieved across a broad scope of alkenes without the need for a transition metal catalyst or a chemical oxidant. Mechanistic data support a dual catalytic role for the aminoxyl serving as both a single-electron oxidant and a radical group transfer agent.
- Siu, Juno C.,Parry, Joseph B.,Lin, Song
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supporting information
p. 2825 - 2831
(2019/02/14)
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- Flat and Efficient H CNN and CNN Pincer Ruthenium Catalysts for Carbonyl Compound Reduction
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The bidentate HCNN dicarbonyl ruthenium complexes trans,cis-[RuCl2(HCNN)(CO)2] (1-3) and trans,cis-[RuCl2(ampy)(CO)2] (1a) were prepared by reaction of [RuCl2(CO)2]n with 1-[6-(4′-methylphenyl)pyridin-2-yl]methanamine, benzo[h]quinoline (HCNN), and 2-(aminomethyl)pyridine (ampy) ligands. Alternatively, the derivatives 1-3 were obtained from the reaction of RuCl3 hydrate with HCO2H and HCNN. The pincer CNN cis-[RuCl(CNN)(CO)2] (4) was isolated from 1 by reaction with NEt3. The monocarbonyl complexes trans-[RuCl2(HCNN)(PPh3)(CO)] (5-7) were synthesized from [RuCl2(dmf)(PPh3)2(CO)] and HCNN ligands, while the diacetate trans-[Ru(OAc)2(HCNN)(PPh3)(CO)] (8) was obtained from [Ru(OAc)2(PPh3)2(CO)]. Carbonylation of cis-[RuCl(CNN)(PPh3)2] with CO afforded the pincer derivatives [RuCl(CNN)(PPh3)(CO)] (9-11). Treatment of 9 with Na[BArf]4 and PPh3 gave the cationic complex trans-[Ru(CNN)(PPh3)2(CO)][BArf4] (12). The dicarbonyl derivatives 1-4, in the presence of PPh3 or PCy3, and the monocarbonyl complexes 5-12 catalyzed the transfer hydrogenation (TH) of acetophenone (a) in 2-propanol at reflux (S/C = 1000-100000 and TOF up to 100000 h-1). Compounds 1-3, with PCy3, and 6 and 8-10 were proven to catalyze the TH of carbonyl compounds, including α,β-unsaturated aldehydes and bulky ketones (S/C and TOF up to 10000 and 100000 h-1, respectively). The derivatives 1-3 with PCy3 and 5 and 6 catalyzed the hydrogenation (HY) of a (H2, 30 bar) at 70 °C (S/C = 2000-10000). Complex 5 was active in the HY of diaryl ketones and aryl methyl ketones, leading to complete conversion at S/C = 10000.
- Giboulot, Steven,Baldino, Salvatore,Ballico, Maurizio,Figliolia, Rosario,P?thig, Alexander,Zhang, Shuanming,Zuccaccia, Daniele,Baratta, Walter
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p. 1127 - 1142
(2019/03/14)
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- A Practical and Stereoselective In Situ NHC-Cobalt Catalytic System for Hydrogenation of Ketones and Aldehydes
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Homogeneous catalytic hydrogenation of carbonyl groups is a synthetically useful and widely applied organic transformation. Sustainable chemistry goals require replacing conventional noble transition metal catalysts for hydrogenation by earth-abundant base metals. Herein, we report how a practical in situ catalytic system generated by easily available pincer NHC precursors, CoCl2, and a base enabled efficient and high-yielding hydrogenation of a broad range of ketones and aldehydes (over 50 examples and a maximum turnover number [TON] of 2,610). This is the first example of NHC-Co-catalyzed hydrogenation of C=O bonds using flexible pincer NHC ligands consisting of a N-H substructure. Diastereodivergent hydrogenation of substituted cyclohexanone derivatives was also realized by fine-tuning of the steric bulk of pincer NHC ligands. Additionally, a bis(NHCs)-Co complex was successfully isolated and fully characterized, and it exhibits excellent catalytic activity that equals that of the in-situ-formed catalytic system. Catalytic hydrogenation is a powerful tool for the reduction of organic compounds in both fine and bulk chemical industries. To improve sustainability, more ecofriendly, inexpensive, and earth-abundant base metals should be employed to replace the precious metals that currently dominate the development of hydrogenation catalysts. However, the majority of the base-metal catalysts that have been reported involve expensive, complex, and often air- and moisture-sensitive phosphine ligands, impeding their widespread application. From a mixture of the stable CoCl2, imidazole salts, and a base, our newly developed catalytic system that formed easily in situ enables efficient and stereoselective hydrogenation of C=O bonds. We anticipate that this easily accessible catalytic system will create opportunities for the design of practical base-metal hydrogenation catalysts. A practical in situ catalytic system generated by a mixture of easily available pincer NHC precursors, CoCl2, and a base enabled highly efficient hydrogenation of a broad range of ketones and aldehydes (over 50 examples and up to a turnover number [TON] of 2,610). Diastereodivergent hydrogenation of substituted cyclohexanone derivatives was also realized in high selectivities. Moreover, the preparation of a well-defined bis(NHCs)-Co complex via this pincer NHC ligand consisting of a N-H substructure was successful, and it exhibits equally excellent catalytic activity for the hydrogenation of C=O bonds.
- Zhong, Rui,Wei, Zeyuan,Zhang, Wei,Liu, Shun,Liu, Qiang
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supporting information
p. 1552 - 1566
(2019/06/14)
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- Influence of the Ionic Liquid on the Activity of a Supported Ionic Liquid Phase FeII Pincer Catalyst for the Hydrogenation of Aldehydes
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The catalytic hydrogenation of different aldehydes to the corresponding alcohols was investigated using an FeII hydride pincer complex as catalyst in the supported ionic liquid phase (SILP) reaction mode. Two different ionic liquids of the type [X4441][NTf2] with X=N or P were applied with mesoporous silica gel as support, which was coated first with a chemisorbed monolayer of the corresponding modified IL to remove acidic surface OH-groups and to prevent IL leaching. Quantitative conversion with turn-over frequencies in the order of 1000 h– 1 were obtained for various aromatic and heteroaromatic aldehydes and highly selective aldehyde reduction was observed also for substrates containing reducible C=C bonds. Aldehydes with longer aliphatic chains or cycloalkyl substituents, however, showed no conversion here, in contrast to a previous study with an imidazolium-based ionic liquid. These differences were ascribed primarily to differences in substrate/ionic liquid interactions. Whereas [N4441][NTf2] and [P4441][NTf2] gave essentially identical results for different substrates in single-batch reactions, prolonged use of the catalyst in repeated reaction cycles lead to a quick drop-off in catalyst activity in [P4441][NTf2], but a continuous, quantitative conversion in [N4441][NTf2].
- Csendes, Zita,Brünig, Julian,Yigit, Nevzat,Rupprechter, Günther,Bica-Schr?der, Katharina,Hoffmann, Helmuth,Kirchner, Karl
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p. 3503 - 3510
(2019/08/12)
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- Highly pH-Dependent Chemoselective Transfer Hydrogenation of α,β-Unsaturated Aldehydes in Water
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The pH-dependent selective Ir-catalyzed hydrogenation of α,β-unsaturated aldehydes was realized in water. Using HCOOH as the hydride donor at low pH, the unsaturated alcohol products were obtained exclusively, while the saturated alcohol products were formed preferentially by employing HCOONa as the hydride donor at high pH. A wide range of functional groups including electron-rich as well as electron-poor substituents on the aryl group of α,β-unsaturated aldehydes can be tolerated, affording the corresponding products in excellent yields with high TOF values. High selectivity and yields were also observed for α,β-unsaturated aldehydes with aliphatic substituents. Our mechanistic investigations indicate that the pH value is critical to the chemoselectivity.
- Luo, Nianhua,Liao, Jianhua,Ouyang, Lu,Wen, Huiling,Liu, Jitian,Tang, Weiping,Luo, Renshi
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p. 3025 - 3031
(2019/08/30)
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- P-CHIRAL PHOSPHINE LIGANDS AND USE THEREOF FOR ASYMMETRIC SYNTHESIS
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The present invention relates to chiral compounds with two optically active phosphorus atoms, chiral transition metal catalysts which comprise these compounds as ligands, a process for preparing the P-chiral compounds and processes for asymmetric synthesis using the chiral transition metal catalysts. The present invention specifically relates to a process for preparing an optically active carbonyl compound by asymmetric hydrogenation of a prochiral α,β-unsaturated carbonyl compound with hydrogen in the presence of an optically active transition metal catalyst according to the invention. Yet more specifically, the present invention relates to a process for the asymmetric hydrogenation of citral, and also a process for preparing optically active menthol.
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Paragraph 0924; 0925; 0928
(2019/07/23)
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- Porous, Naturally Derived Hafnium Phytate for the Highly Chemoselective Transfer Hydrogenation of Aldehydes with Other Reducible Moieties
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Both the utilization of naturally occurring compounds to prepare functional materials and the selective conversion of aldehydes with other reducible moieties (ORMs) are very attractive topics. Herein, we synthesized a novel porous material, hafnium phytate (Hf-Phy), by using naturally derived sodium phytate as the building block. Hf-Phy has plenty of mesopores centered around 11.8 nm. Hf-Phy showed excellent performance for the transfer hydrogenation of aldehydes with ORMs by using 2-propanol as the hydrogen source with high selectivities (95–100 %) for alcohols without reducing ORMs. Systematic studies suggested that the oxophilicity of Hf4+ and the basicity and structure of Hf-Phy contributed significantly to the excellent performance. Additionally, Hf-Phy could be used over at least five cycles without any decrease in activity or selectivity.
- Song, Jinliang,Xue, Zhimin,Xie, Chao,Wu, Haoran,Liu, Shuaishuai,Zhang, Lujun,Han, Buxing
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p. 725 - 730
(2018/01/22)
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- Sulfonic acid anchored on silica, SiO2@SO3H: A superior solid acid catalyst for quick and solvent-free reductive-deoxygenation of ketones with NaBH3CN
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NaBH3CN as a modified hydroborate agent and due to a strong withdrawing CN group does not show any reducing ability to reduce functional groups in the absence of acidic media (pH ~ 3–4). In this study, the immobilized sulfonic acid on silica, SiO2@SO3H, was prepared and applied as a new solid acid catalyst for extremely enhancing the reducing ability of NaBH3CN. The influence of SiO2@SO3H was highlighted by performing the quick and green reduction of structurally diverse carbonyl compounds involving aldehydes, ketones, α,β-unsaturated enals and enones, α-diketones, and acyloins to the corresponding alcohols or alkanes with NaBH3CN. By the NaBH3CN/SiO2@SO3H system, aldehydes were reduced to the corresponding alcohols and ketonic compounds to alkanes as reductive-deoxygenation products. All reduction reactions were carried out within 3 min at room temperature and under solvent-free conditions to afford the products in high to excellent yields (90–98%).
- Zeynizadeh, Behzad,Kouhkan, Mehri
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p. 1521 - 1528
(2018/11/23)
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- Mechanistic Investigation of Bis(imino)pyridine Manganese Catalyzed Carbonyl and Carboxylate Hydrosilylation
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We recently reported a bis(imino)pyridine (or pyridine diimine, PDI) manganese precatalyst, (Ph2PPrPDI)Mn (1), that is active for the hydrosilylation of ketones and dihydrosilylation of esters. In this contribution, we reveal an expanded scope for 1-mediated hydrosilylation and propose two different mechanisms through which catalysis is achieved. Aldehyde hydrosilylation turnover frequencies (TOFs) of up to 4900 min-1 have been realized, the highest reported for first row metal-catalyzed carbonyl hydrosilylation. Additionally, 1 has been shown to mediate formate dihydrosilylation with leading TOFs of up to 330 min-1. Under stoichiometric and catalytic conditions, addition of PhSiH3 to (Ph2PPrPDI)Mn was found to result in partial conversion to a new diamagnetic hydride compound. Independent preparation of (Ph2PPrPDI)MnH (2) was achieved upon adding NaEt3BH to (Ph2PPrPDI)MnCl2 and single-crystal X-ray diffraction analysis revealed this complex to possess a capped trigonal bipyramidal solid-state geometry. When 2,2,2-trifluoroacetophenone was added to 1, radical transfer yielded (Ph2PPrPDI·)Mn(OC·(Ph)(CF3)) (3), which undergoes intermolecular C-C bond formation to produce the respective Mn(II) dimer, [(μ-O,Npy-4-OC(CF3)(Ph)-4-H-Ph2PPrPDI)Mn]2 (4). Upon finding 3 to be inefficient and 4 to be inactive, kinetic trials were conducted to elucidate the mechanisms of 1- and 2-mediated hydrosilylation. Varying the concentration of 1, substrate, and PhSiH3 revealed a first order dependence on each reagent. Furthermore, a kinetic isotope effect (KIE) of 2.2 ± 0.1 was observed for 1-catalyzed hydrosilylation of diisopropyl ketone, while a KIE of 4.2 ± 0.6 was determined using 2, suggesting 1 and 2 operate through different mechanisms. Although kinetic trials reveal 1 to be the more active precatalyst for carbonyl hydrosilylation, a concurrent 2-mediated pathway is more efficient for carboxylate hydrosilylation. Considering these observations, 1-catalyzed hydrosilylation is believed to proceed through a modified Ojima mechanism, while 2-mediated hydrosilylation occurs via insertion.
- Mukhopadhyay, Tufan K.,Rock, Christopher L.,Hong, Mannkyu,Ashley, Daniel C.,Groy, Thomas L.,Baik, Mu-Hyun,Trovitch, Ryan J.
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p. 4901 - 4915
(2017/04/11)
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- Efficient Water Reduction with sp3-sp3 Diboron(4) Compounds: Application to Hydrogenations, H–D Exchange Reactions, and Carbonyl Reductions
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A series of crystalline sp3-sp3 diboron(4) compounds were synthesized and shown to promote the facile reduction of water with dihydrogen formation. The application of these diborons as simple and effective dihydrogen and dideuterium sources was demonstrated by conducting a series of selective reductions of alkynes and alkenes, and hydrogen–deuterium exchange reactions using two-chamber reactors. Finally, as the water reduction reaction generates an intermediate borohydride species, a range of aldehydes and ketones were reduced by using water as the hydride source.
- Flinker, Mathias,Yin, Hongfei,Juhl, René W.,Eikeland, Espen Z.,Overgaard, Jacob,Nielsen, Dennis U.,Skrydstrup, Troels
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supporting information
p. 15910 - 15915
(2017/11/23)
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- Umpolung of protons from H2O: A metal-free chemoselective reduction of carbonyl compounds: Via B2pin2/H2O systems
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H2O is routinely described as a proton donor, however, in the presence of diboron compounds, the umpolung reaction of H2O under metal-free conditions was successfully developed, which could afford hydride species, leading to a highly efficient and chemoselective reduction of CO bonds. This strategy exhibits excellent chemoselectivities toward carbonyl groups in the presence of ester, olefin, halogen, thioether, sulfonyl, cyano as well as heteroaromatic groups.
- Xuan, Qingqing,Zhao, Cong,Song, Qiuling
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supporting information
p. 5140 - 5144
(2017/07/11)
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- Synthesis, characterization and performance of bifunctional catalysts for the synthesis of menthol from citronellal
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The synthesis of a series of bifunctional catalysts (1 wt% Pt/W-TUD-1 (Technische Universiteit Delft-1) and 1 wt% Pt/WO3/TUD-1) with different tungsten loadings (5-30 wt% WO3) is described. They were characterized using ICP-OES, INAA, N2 physisorption, XRD and TEM. Their catalytic performance (activity and selectivity) was evaluated in the two-step catalytic synthesis of menthol from citronellal using kinetic analysis. Introducing tungsten during the TUD-1 synthesis results in a high WO3 dispersion, essential for the acidity of the catalyst. High tungsten dispersion is also critical for the Pt hydrogenation activity. Therefore, high dispersion combined with optimal tungsten loading resulted in the highest catalytic activity. The best performing catalyst was 1 wt% Pt/W-TUD-1 (silicon to tungsten ratio of 30), with the highest yields of menthol (96%).
- Ten Dam,Ramanathan,Djanashvili,Kapteijn,Hanefeld
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p. 12041 - 12053
(2017/03/08)
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- N,N,O-Tridentate Mixed Lithium-Magnesium and Lithium-Aluminum Complexes: Synthesis, Characterization, and Catalytic Activities
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The syntheses and crystal structures of a series of heterobimetallic Li/Mg and Li/Al complexes prepared from an N,N,O-tridentate ligand are described. The ligand HOC(CH2)5CH2N(Me)CH2CH2NMe2 (LH) and nBu2Mg were used to synthesize the homometallic magnesium alkoxide [{LMgOC(CH2)5CH2N(Me)CH2CH2NMe2}2] (1), which was reacted with nBuLi to afford the lithium alkylmagnesiate [{Bu2Mg{LiOC(CH2)5CH2N(Me)CH2CH2NMe2}}2] (2). Complex 2 was then hydrolyzed to produce [{BuMgOLi{LiOC(CH2)5CH2N(Me)CH2CH2NMe2}2}2] (3). The sequential reaction of LH in diethyl ether with RAlMe2 (R = Me, Cl) and nBuLi aforded two lithium aluminate complexes containing a polymeric structure of one-dimensional chains [{?LiOC(CH2)5CH2N(Me)CH2CH2NMe2}Al(Me)(n-Bu)CH3?}n] (4) and [{?LiOC(CH2)5CH2N(Me)CH2CH2NMe2}Al(n-Bu)2CH2?}n] (5), respectively. Each of the complexes 1-5 was structurally characterized and tested for its capability to catalyze Meerwein-Ponndorf-Verley (MPV) reactions. Heterobimetallic complexes 2 and 3 exhibited catalytic activities better than those of homometallic magnesium complex 1 and heterobimetallic lithium aluminate complexes 4 and 5 for MPV reactions.
- Hua, Yupeng,Guo, Zhiqiang,Han, Hongfei,Wei, Xuehong
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p. 877 - 883
(2017/04/21)
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- Synthesis and crystal structures of guanidinatoaluminum complexes and catalytic study for MPV reduction
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Treatment of a secondary amine (piperidine or N-benzylmethylamine) with sequentially trimethylaluminum and carbodiimide CyN[dbnd]C[dbnd]NCy in a molar ratio of 1:1:1 afforded two mononuclear guanidinatoaluminum complexes, [{(C5H10N)C(NCy)2}AlMe2] (1) and. [{(Bz(Me)N)C(NCy)2}AlMe2] (2). Introducing dry oxygen slowly into the solution of 1 or 2, [{(C5H10N)C(NCy)2}AlMe(μ-OMe)]2 (3) and [{(Bz(Me)N)C(NCy)2}AlMe(μ-OMe)]2 (4) were obtained, respectively. Both of 3 and 4 were also prepared by treatment of piperidine or N-benzylmethylamine with trimethylaluminum and carbodiimide CyN[dbnd]C[dbnd]NCy in the presence of O2. The complexes 1–4 were characterized by 1H, 13C NMR spectra and single crystal X-ray diffraction analysis. 1–4 were also used to catalyze the Meerwein–Ponndorf–Verley (MPV) reaction.
- Han, Hongfei,Guo, Zhiqiang,Zhang, Shaofeng,Hua, Yupeng,Wei, Xuehong
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p. 214 - 219
(2017/07/18)
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- Selective hydrogenation of unsaturated carbonyls by Ni-Fe-based alloy catalysts
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Ni-Fe alloy catalysts prepared by a simple hydrothermal method and subsequent H2 treatment exhibited the greatest activity and selectivity for the hydrogenation of biomass-derived furfural to furfuryl alcohol among the examined second metals, such as Al, Ga, In, Co, and Ti. This work reveals that the alloying of Ni and Fe is a key factor in achieving highly selective hydrogenation of the CO moiety in unsaturated carbonyl substrates. We found that decreasing the temperature of H2 treatment (i.e. decreasing the crystallite size), e.g. Ni-Fe(2)HT-573 K (TOF = 952 h-1), increased the activity compared to that over Ni-Fe(2)HT-673 (TOF = 375 h-1) for furfural hydrogenation. This result suggests that a low-coordinated Ni-Fe alloy was imperative for the catalytic cycle. Moreover, the effect of the metal/support interface was critical; despite the high catalytic performance of Ni-Fe/TiO2, Ni-Fe/Al2O3, and Ni-Fe/CeO2, Ni-Fe supported on SiO2, taeniolite, and hydrotalcite catalysts were ineffective. Vibrational studies using FT-IR measurement confirmed that furfural was physically adsorbed on the surface of the Ni-Fe alloy catalyst via an η1(O) configuration. The synthetic scope of the Ni-Fe catalytic system was very broad; various types of unsaturated carbonyls, such as unsaturated aromatics, unconjugated aliphatics, and a large substituent, were selectively converted into the corresponding unsaturated alcohols.
- Putro, Wahyu S.,Kojima, Takashi,Hara, Takayoshi,Ichikuni, Nobuyuki,Shimazu, Shogo
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p. 3637 - 3646
(2017/08/21)
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- Selective hydrogenation of citral by noble metals supported on carbon xerogels: Catalytic performance and stability
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A series of monometallic Pt, Ir and Ru-catalysts deposited on carbon xerogel microspheres was prepared, exhaustively characterized and used in the selective hydrogenation of citral. A similar metal particle size is obtained in all cases after He-pretreatment, allowing the comparison between metals; the catalytic activity increases in the sense Ir 2-flow leading to an important loss of activity, especially for Ru-catalysts. Pt and Ir-catalysts are more selective than Ru-catalysts, reaching selectivity values to unsaturated alcohols of around 80%. Thus, in terms of yields to these valuable products Pt-catalysts seem to be the most appropriate active phase. Nevertheless, reutilization experiments showed that Ir-catalyst maintained a good performance while a severe deactivation is observed for Pt-catalysts. This fact is discussed on the basis of the different nature of the deposits formed during reaction.
- Bailón-García, Esther,Carrasco-Marín, Francisco,Pérez-Cadenas, Agustín F.,Maldonado-Hódar, Francisco J.
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- Long-chain NHC-stabilized RuNPs as versatile catalysts for one-pot oxidation/hydrogenation reactions
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The synthesis and catalytic activity of long-chain NHC-stabilized RuNPs are presented. Full characterization of these novel nanostructures including surface state studies show that the ligand influences the number and the location of Ru active sites which impacts the NP catalytic activity, especially in hydrogenation reactions. The high stability and versatility of these nanosystems make them successful catalysts for both oxidation and hydrogenation reactions that can even be performed successively in a one pot-fashion.
- Martínez-Prieto,Ferry,Rakers,Richter,Lecante,Philippot,Chaudret,Glorius
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supporting information
p. 4768 - 4771
(2016/04/09)
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- Loop-Grafted Old Yellow Enzymes in the Bienzymatic Cascade Reduction of Allylic Alcohols
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The enzymatic reduction of C=C bonds in allylic alcohols with Old Yellow Enzymes represents a challenging task, due to insufficient activation through the hydroxy group. In our work, we coupled an alcohol dehydrogenase with three wild-type ene reductases - namely nicotinamide-dependent cyclohex-2-en-1-one reductase (NCR) from Zymomonas mobilis, OYE1 from Saccharomyces pastorianus and morphinone reductase (MR) from Pseudomonas putida M10 - and four rationally designed β/α loop variants of NCR in the bienzymatic cascade hydrogenation of allylic alcohols. Remarkably, the wild type of NCR was not able to catalyse the cascade reaction whereas MR and OYE1 demonstrated high to excellent activities. Through the rational loop grafting of two intrinsic β/α surface loop regions near the entrance of the active site of NCR with the corresponding loops from OYE1 or MR we successfully transferred the cascade reduction activity from one family member to another. Further we observed that loop grafting revealed certain influences on the interaction with the nicotinamide cofactor.
- Reich, Sabrina,Nestl, Bettina M.,Hauer, Bernhard
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p. 561 - 565
(2016/04/26)
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- Hydrogenation of Aldehydes Catalyzed by an Available Ruthenium Complex
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A readily available ruthenium(II) catalyst was developed for the catalytic hydrogenation of aldehydes with a TON (turnover number) up to 340000. It can be performed without base and solvent, showing highly industrial potential. High chemoselectivity can be achieved in the presence of alkenyl and ketone groups. Further application of this protocol in glucose reduction showed good efficiency. Theoretical studies revealed that the rate-determining step is the hydrogenation step, not the carboxylate-assisted H2 activation step.
- Tan, Xuefeng,Wang, Guozhen,Zhu, Ziyue,Ren, Conghui,Zhou, Jinping,Lv, Hui,Zhang, Xiaoyong,Chung, Lung Wa,Zhang, Lina,Zhang, Xumu
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supporting information
p. 1518 - 1521
(2016/05/02)
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- BENZO[H]QUINOLINE LIGANDS AND COMPLEXES THEREOF
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The present invention provides substituted tridentate benzo[h]quinoline ligands and complexes thereof. The invention also provides the preparation of the ligands and the respective complexes, as well as to processes for using the complexes in catalytic reactions.
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Page/Page column 85-87
(2016/12/22)
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- Selective Catalytic Hydrogenations of Nitriles, Ketones, and Aldehydes by Well-Defined Manganese Pincer Complexes
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Hydrogenations constitute fundamental processes in organic chemistry and allow for atom-efficient and clean functional group transformations. In fact, the selective reduction of nitriles, ketones, and aldehydes with molecular hydrogen permits access to a green synthesis of valuable amines and alcohols. Despite more than a century of developments in homogeneous and heterogeneous catalysis, efforts toward the creation of new useful and broadly applicable catalyst systems are ongoing. Recently, Earth-abundant metals have attracted significant interest in this area. In the present study, we describe for the first time specific molecular-defined manganese complexes that allow for the hydrogenation of various polar functional groups. Under optimal conditions, we achieve good functional group tolerance, and industrially important substrates, e.g., for the flavor and fragrance industry, are selectively reduced.
- Elangovan, Saravanakumar,Topf, Christoph,Fischer, Steffen,Jiao, Haijun,Spannenberg, Anke,Baumann, Wolfgang,Ludwig, Ralf,Junge, Kathrin,Beller, Matthias
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supporting information
p. 8809 - 8814
(2016/07/29)
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- Stable and Inert Cobalt Catalysts for Highly Selective and Practical Hydrogenation of C≡N and C=O Bonds
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Novel heterogeneous cobalt-based catalysts have been prepared by pyrolysis of cobalt complexes with nitrogen ligands on different inorganic supports. The activity and selectivity of the resulting materials in the hydrogenation of nitriles and carbonyl compounds is strongly influenced by the modification of the support and the nitrogen-containing ligand. The optimal catalyst system ([Co(OAc)2/Phenα-Al2O3]-800 = Cat. E) allows for efficient reduction of both aromatic and aliphatic nitriles including industrially relevant dinitriles to primary amines under mild conditions. The generality and practicability of this system is further demonstrated in the hydrogenation of diverse aliphatic, aromatic, and heterocyclic ketones as well as aldehydes, which are readily reduced to the corresponding alcohols.
- Chen, Feng,Topf, Christoph,Radnik, J?rg,Kreyenschulte, Carsten,Lund, Henrik,Schneider, Matthias,Surkus, Annette-Enrica,He, Lin,Junge, Kathrin,Beller, Matthias
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supporting information
p. 8781 - 8788
(2016/08/02)
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