591-23-1Relevant articles and documents
Enhanced Hydrodeoxygenation of m-Cresol over Bimetallic Pt-Mo Catalysts through an Oxophilic Metal-Induced Tautomerization Pathway
Robinson, Allison,Ferguson, Glen Allen,Gallagher, James R.,Cheah, Singfoong,Beckham, Gregg T.,Schaidle, Joshua A.,Hensley, Jesse E.,Medlin, J. Will
, p. 4356 - 4368 (2016)
Supported bimetallic catalysts consisting of a noble metal (e.g., Pt) and an oxophilic metal (e.g., Mo) have received considerable attention for the hydrodeoxygenation of oxygenated aromatic compounds produced from biomass fast pyrolysis. Here, we report that PtMo can catalyze m-cresol deoxygenation via a pathway involving an initial tautomerization step. In contrast, the dominant mechanism on monometallic Pt/Al2O3 was found to be sequential Pt-catalyzed ring hydrogenation followed by dehydration on the support. Bimetallic Pt10Mo1 and Pt1Mo1 catalysts were found to produce the completely hydrogenated and deoxygenated product, methylcyclohexane (MCH), with much higher yields than monometallic Pt catalysts with comparable metal loadings and surface areas. Over an inert carbon support, MCH formation was found to be slow over monometallic Pt catalysts, while deoxygenation was significant for PtMo catalysts even in the absence of an acidic support material. Experimental studies of m-cresol deoxygenation together with density functional theory calculations indicated that Mo sites on the PtMo bimetallic surface dramatically lower the barrier for m-cresol tautomerization and subsequent deoxygenation. The accessibility of this pathway arises from the increased interaction between the oxygen of m-cresol and the Mo sites in the Pt surface. This interaction significantly alters the configuration of the precursor and transition states for tautomerization. A suite of catalyst characterization techniques including X-ray absorption spectroscopy (XAS) and temperature-programmed reduction (TPR) indicate that Mo was present in a reduced state on the bimetallic surface under conditions relevant for reaction. Overall, these results suggest that the use of bifunctional metal catalysts can result in new reaction pathways that are unfavorable on monometallic noble metal catalysts.
Dispersed copper oxide: A multifaceted tool in catalysis
Scotti, Nicola,Monticelli, Damiano,Zaccheria, Federica
, p. 194 - 200 (2012)
The preparation of highly dispersed copper oxide over different supports by means of a simple and versatile technique makes available a family of catalysts active for different kind of transformations. The proper choice of the inorganic matrix used as the support shapes the electronic properties of the deposited phase and, as a consequence, its catalytic behavior. Cu(0), Cu(δ+) and CuO nanoparticles resulted to be very active, respectively in hydrogenation reactions, NOx selective catalytic reduction by hydrocarbons and acid catalyzed formation of asymmetrical ethers starting from alcohols.
Heterogeneous Hydroxyl-Directed Hydrogenation: Control of Diastereoselectivity through Bimetallic Surface Composition
Shumski, Alexander J.,Swann, William A.,Escorcia, Nicole J.,Li, Christina W.
, p. 6128 - 6134 (2021/05/29)
Directed hydrogenation, in which product selectivity is dictated by the binding of an ancillary directing group on the substrate to the catalyst, is typically catalyzed by homogeneous Rh and Ir complexes. No heterogeneous catalyst has been able to achieve equivalently high directivity due to a lack of control over substrate binding orientation at the catalyst surface. In this work, we demonstrate that Pd-Cu bimetallic nanoparticles with both Pd and Cu atoms distributed across the surface are capable of high conversion and diastereoselectivity in the hydroxyl-directed hydrogenation reaction of terpinen-4-ol. We postulate that the OH directing group adsorbs to the more oxophilic Cu atom while the olefin and hydrogen bind to adjacent Pd atoms, thus enabling selective delivery of hydrogen to the olefin from the same face as the directing group with a 16:1 diastereomeric ratio.
Catalytic transfer hydrogenation of 4-O-5 models in lignin-derived compounds to cycloalkanes over Ni-based catalysts
Chen, Changzhou,Liu, Peng,Xia, Haihong,Zhou, Minghao,Jiang, Jianchun
, p. 582 - 591 (2020/12/01)
There is an urgent need to develop a selective hydrogenolysis of Caryl-O bonds in lignin to produce valued-added chemicals and fuels. Recently, hydrogen has been used in the hydrogenation reaction, which hides inevitable danger and is not economical. Therefore, isopropanol, as a hydrogen-donor solvent, is employed for aryl ether hydrogenolysis in lignin models over nickel supported on a carbon nanotube (CNT). Except for aromatic ether (4-O-5), the Ni/CNT catalyst is also found to be suitable for alkyl-aryl ether (α-O-4 and β-O-4) cleavage in control experiments. The physicochemical characterizations were carried out by means of H2-temperature-programmed reduction, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy analyses. The catalyst can be magnetically recovered and efficiently reused for five consecutive recycling tests in the transfer hydrogenation of aromatic ethers. A mechanism study indicated that the hydrogenolysis cleavage of the ether bond is the first step in the reaction process, and hydrogenation of aromatic rings is only a successive step in which phenol and benzene are intermediate states and are then further hydrogenated. Furthermore, it has been demonstrated that aryl groups play an important role in the hydrogenation of phenol in the competitive catalytic hydrogenation reaction of phenol.
Manganese-catalyzed homogeneous hydrogenation of ketones and conjugate reduction of α,β-unsaturated carboxylic acid derivatives: A chemoselective, robust, and phosphine-free in situ-protocol
Topf, Christoph,Vielhaber, Thomas
, (2021/07/10)
We communicate a user-friendly and glove-box-free catalytic protocol for the manganese-catalyzed hydrogenation of ketones and conjugated C[dbnd]C[sbnd]bonds of esters and nitriles. The respective catalyst is readily assembled in situ from the privileged [Mn(CO)5Br] precursor and cheap 2-picolylamine. The catalytic transformations were performed in the presence of t-BuOK whereby the corresponding hydrogenation products were obtained in good to excellent yields. The described system offers a brisk and atom-efficient access to both secondary alcohols and saturated esters avoiding the use of oxygen-sensitive and expensive phosphine-based ligands.
Application of robust ketoreductase from Hansenula polymorpha for the reduction of carbonyl compounds
Petrovi?ová, Tatiana,Gyuranová, Dominika,Pl?, Michal,Myrtollari, Kamela,Smonou, Ioulia,Rebro?, Martin
, (2021/02/05)
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.
Discovery of New Carbonyl Reductases Using Functional Metagenomics and Applications in Biocatalysis
Newgas, Sophie A.,Jeffries, Jack W. E.,Moody, Thomas S.,Ward, John M.,Hailes, Helen C.
, p. 3044 - 3052 (2021/04/26)
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.).
Effects of Water Addition on the Conversion of o-Cresol in the Presence of In Situ Ni–Mo Sulfide Catalysts
Kniazeva,Kuchinskaya,Erasheva
, p. 682 - 687 (2021/04/09)
Abstract: Ni-Mo sulfide systems generated in situ from precursor salts were used for the hydrodeoxygenation of o-cresol. After the reaction, the catalysts were recovered and analyzed by transmission electron microscopy and X-ray photoelectron spectroscopy. It was shown that the addition of water into the reaction system affects the composition of the o-cresol conversion product due to a change in the texture and phase composition of the surface layer of the in situ sulfide particles.
Aliphatic C–H hydroxylation activity and durability of a nickel complex catalyst according to the molecular structure of the bis(oxazoline) ligands
Hikichi, Shiro,Izumi, Takashi,Matsuba, Naki,Nakazawa, Jun
, (2021/07/13)
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.
Expedient Synthesis of Bridged Bicyclic Nitrogen Scaffolds via Orthogonal Tandem Catalysis
Bheemireddy, Narendraprasad Reddy,Biswas, Sovan,Evano, Gwilherm,Maes, Bert U. W.,Van Steijvoort, Ben F.,Waeterschoot, Marjo
, p. 21988 - 21996 (2021/08/13)
Bridged nitrogen bicyclic skeletons have been accessed via unprecedented site- and diastereoselective orthogonal tandem catalysis from readily accessible reactants in a step economic manner. Directed Pd-catalyzed γ-C(sp3)-H olefination of aminocyclohexane with gem-dibromoalkenes, followed by a consecutive intramolecular Cu-catalyzed amidation of the 1-bromo-1-alkenylated product delivers the interesting normorphan skeleton. The tandem protocol can be applied on substituted aminocyclohexanes and aminoheterocycles, easily providing access to the corresponding substituted, aza- and oxa-analogues. The Cu catalyst of the Ullmann-Goldberg reaction additionally avoids off-cycle Pd catalyst scavenging by alkenylated reaction product. The picolinamide directing group stabilizes the enamine of the 7-alkylidenenormorphan, allowing further product post functionalizations. Without Cu catalyst, regio- and diastereoselective Pd-catalyzed γ-C(sp3)-H olefination is achieved.
