4358-88-7Relevant academic research and scientific papers
Copper-Carbene Intermediates in the Copper-Catalyzed Functionalization of O-H Bonds
Pereira, Ana,Champouret, Yohan,Martín, Carmen,álvarez, Eleuterio,Etienne, Michel,Belderraín, Tomás R.,Pérez, Pedro J.
, p. 9769 - 9775 (2015)
Copper-carbene [TpxCu=C(Ph)(CO2Et)] and copper-diazo adducts [TpxCu{η1-N2C(Ph)(CO2Et)}] have been detected and characterized in the context of the catalytic functionalization of O-H bonds through carbene insertion by using N2=C(Ph)(CO2Et) as the carbene source. These are the first examples of these type of complexes in which the copper center bears a tridentate ligand and displays a tetrahedral geometry. The relevance of these complexes in the catalytic cycle has been assessed by NMR spectroscopy, and kinetic studies have demonstrated that the N-bound diazo adduct is a dormant species and is not en route to the formation of the copper-carbene intermediate.
One-step room-temperature synthesis of [Al]MCM-41 materials for the catalytic conversion of phenylglyoxal to ethylmandelate
Wang, Zichun,Jiang, Yijiao,Rachwalik, Rafal,Liu, Zhongwen,Shi, Jeffrey,Hunger, Michael,Huang, Jun
, p. 3889 - 3896 (2013)
Mesoporous [Al]MCM-41 materials with nSi/nAl ratios of 15 to 50 suitable for the direct catalytic conversion of phenylglyoxal to ethylmandelate have been successfully synthesized at room temperature within 1 h. The surface areas and pore sizes of the obtained [Al]MCM-41 materials are in the ranges of 1005-1246 m2 g-1 and 3.44-3.99 nm, respectively, for the different nSi/nAl ratios. For all [Al]MCM-41 catalysts, most of the Al species were tetrahedrally coordinated with Si in the next coordination sphere of atoms. 1H and 13C magic-angle spinning NMR spectroscopic investigations indicated that the acid strength of the SiOH groups on these [Al]MCM-41 catalysts and the density of these surface sites are enhanced with increasing Al content in the synthesis gels. These surface sites with enhanced acid strength were found to be catalytically active sites for phenylglyoxal conversion. The [Al]MCM-41 material with nSi/nAl=15 showed the highest phenylglyoxal conversion (93.4 %) and selectivity to ethylmandelate (96.9 %), whereas the [Al]MCM-41 material with nSi/nAl=50 reached the highest turnover frequency (TOF=99.3 h-1). This is a much better catalytic performance than that of a dealuminated zeolite Y (TOF=1.7 h-1) used as a reference catalyst, which is explained by lower reactant transport limitations in mesoporous materials than that in the microporous zeolite. Mesopores flex their catalytic muscles: Mesoporous [Al]MCM-41 materials with nSi/nAl ratios of 15 to 50 suitable for the direct catalytic conversion of phenylglyoxal to ethylmandelate were successfully synthesized at room temperature within 1 h. Copyright
Strongly enhanced acidity and activity of amorphous silica–alumina by formation of pentacoordinated AlV species
Wang, Zichun,Jiang, Yijiao,Jin, Fangzhu,Stampfl, Catherine,Hunger, Michael,Baiker, Alfons,Huang, Jun
, p. 1 - 7 (2019)
Tailoring high-performance aluminosilicates plays a key role in the efficient and clean production of high-value chemicals. Recent work reveals that pentacoordinated Al (AlV) species can significantly enhance the Br?nsted acidity of amorphous silica–alumina (ASA), compared with that typically dominated by tetracoordinated Al species. However, the controlled synthesis of AlV-rich ASAs is challenging. Employing xylene as the solvent in a flame-spray pyrolysis process, we synthesized AlV-rich ASAs successfully. The high combustion enthalpy of xylene (36.9 kJ/ml) results in a high flame temperature, promoting the formation and distribution of metastable AlV species in the silica network forming Br?nsted acid sites. This provides a promising route for the controlled synthesis of AlV-rich ASAs with higher Br?nsted acidity. As an example, AlV-rich ASAs are shown to exhibit superior catalytic performance in phenylglyoxal conversion to ethyl mandelate in ethanol compared with that achieved with other acid catalysts, attaining an ethyl mandelate yield of 99.8%.
Tunable System for Electrochemical Reduction of Ketones and Phthalimides
Chen, Gong,Qiao, Tianjiao,Wang, Yaxin,Zhang, Jian,Zhao, Jianyou
supporting information, p. 3297 - 3302 (2021/10/14)
Herein, we report an efficient, tunable system for electrochemical reduction of ketones and phthalimides at room temperature without the need for stoichiometric external reductants. By utilizing NaN3 as the electrolyte and graphite felt as both the cathode and the anode, we were able to selectively reduce the carbonyl groups of the substrates to alcohols, pinacols, or methylene groups by judiciously choosing the solvent and an acidic additive. The reaction conditions were compatible with a diverse array of functional groups, and phthalimides could undergo one-pot reductive cyclization to afford products with indolizidine scaffolds. Mechanistic studies showed that the reactions involved electron, proton, and hydrogen atom transfers. Importantly, an N3/HN3 cycle operated as a hydrogen atom shuttle, which was critical for reduction of the carbonyl groups to methylene groups.
Biocatalysed reductions of α-ketoesters employing CyreneTM as cosolvent
de Gonzalo, Gonzalo
, (2021/02/26)
The search for novel reaction media with environmental friendly properties is an area of great interest in enzyme catalysis. Water is the medium of biocatalysed processes, but due to its properties, sometimes the presence of organic (co)solvents is required. CyreneTM represents one of the newest approaches to this medium engineering. This polar solvent has been employed for the first time in biocatalysed reductions employing purified alcohol dehydrogenases. A set of α-ketoesters has been reduced to the corresponding chiral α-hydroxyesters with high conversions and optical purities, being possible to obtain good results at Cyrene contents of 30% v/v and working at substrate concentrations of 1.0 M in presence of 2.5% v/v of this solvent. At this concentration, the presence of Cyrene has a beneficial effect in the bioreduction conversion.
Preparation of Organic Nitrates from Aryldiazoacetates and Fe(NO3)3·9H2O
Thurow, Samuel,Fernandes, Alessandra A. G.,Quevedo-Acosta, Yovanny,De Oliveira, Matheus F.,De Oliveira, Marcelo G.,Jurberg, Igor D.
, p. 6909 - 6913 (2019/09/12)
A thermal protocol is reported for the formal insertion of nitric acid into aryldiazoacetates using Fe(NO3)3·9H2O. This strategy is mild and high yielding and allows the preparation of a large variety of members of an unprecedented family of organic nitrates. The nitrate group can be also readily transformed into other functional groups and heterocyclic moieties and can possibly allow new biological explorations of untapped potential associated with their NO-releasing ability.
Exploiting Cofactor Versatility to Convert a FAD-Dependent Baeyer–Villiger Monooxygenase into a Ketoreductase
Xu, Jian,Peng, Yongzhen,Wang, Zhiguo,Hu, Yujing,Fan, Jiajie,Zheng, He,Lin, Xianfu,Wu, Qi
supporting information, p. 14499 - 14503 (2019/09/17)
Cyclohexanone monooxygenases (CHMOs) show very high catalytic specificity for natural Baeyer–Villiger (BV) reactions and promiscuous reduction reactions have not been reported to date. Wild-type CHMO from Acinetobacter sp. NCIMB 9871 was found to possess an innate, promiscuous ability to reduce an aromatic α-keto ester, but with poor yield and stereoselectivity. Structure-guided, site-directed mutagenesis drastically improved the catalytic carbonyl-reduction activity (yield up to 99 %) and stereoselectivity (ee up to 99 %), thereby converting this CHMO into a ketoreductase, which can reduce a range of differently substituted aromatic α-keto esters. The improved, promiscuous reduction activity of the mutant enzyme in comparison to the wild-type enzyme results from a decrease in the distance between the carbonyl moiety of the substrate and the hydrogen atom on N5 of the reduced flavin adenine dinucleotide (FAD) cofactor, as confirmed using docking and molecular dynamics simulations.
Cobalt-Catalyzed Transfer Hydrogenation of α-Ketoesters and N-Cyclicsulfonylimides Using H2O as Hydrogen Source
Gao, Yang,Zhang, Xuexin,Laishram, Ronibala Devi,Chen, Jingchao,Li, Kangkui,Zhang, Keyang,Zeng, Guangzhi,Fan, Baomin
supporting information, p. 3991 - 3997 (2019/08/02)
A Co-catalyzed effective transfer hydrogenation of various α-ketoesters and N-cyclicsulfonylimides by safe and environmentally benign H2O as hydrogen source is described. The reaction used easily available and easy to handle zinc metal as a reductant. Interestingly, the catalytic system does not require ligand for reduction of N-cyclicsulfonylimides. (Figure presented.).
Electrochemical Hydrogenation with Gaseous Ammonia
Li, Jin,He, Lingfeng,Liu, Xu,Cheng, Xu,Li, Guigen
supporting information, p. 1759 - 1763 (2019/01/16)
As a carbon-free and sustainable fuel, ammonia serves as high-energy-density hydrogen-storage material. It is important to develop new reactions able to utilize ammonia as a hydrogen source directly. Herein, we report an electrochemical hydrogenation of alkenes, alkynes, and ketones using ammonia as the hydrogen source and carbon electrodes. A variety of heterocycles and functional groups, including for example sulfide, benzyl, benzyl carbamate, and allyl carbamate were well tolerated. Fast stepwise electron transfer and proton transfer processes were proposed to account for the transformation.
Mild and efficient rhodium-catalyzed deoxygenation of ketones to alkanes
Argouarch, Gilles
supporting information, p. 11041 - 11044 (2019/07/31)
A new and simple method for the deoxygenation of ketones to alkanes is presented. Most substrates are reduced under mild conditions by triethylsilane in the presence of catalytic amounts of [Rh(μ-Cl)(CO)2]2. This system selectively provides the methylene hydrocarbons in good to excellent yields starting from acetophenones and diaryl ketones. A rapid examination of the reaction pathway suggests that the ketone is first converted into an alcohol, which then undergoes hydrogenolysis to give the alkane.
