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.
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.
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.
