Search results for "Aldehyde"
showing 10 items of 915 documents
Dual stereocontrolled alkylation of aldehydes with polystyrene-supported nickel complexes derived from α-amino amides
2015
Nickel(II) complexes derived from α-amino amide ligands anchored to gel-type and monolithic polymers act as efficient catalysts for the enantioselective addition of dialkylzinc reagents to aldehydes. Similar to the analogous homogeneous systems, dual stereocontrol in addition products can be achieved by controlling the stoichiometry of the immobilized nickel complex. Aromatic and aliphatic aldehydes were alkylated in good yields with enantioselectivities comparable to those obtained with the homogeneous analogues. These polymer-supported catalysts offer significant advantages as no metal leaching is observed and they can be easily recovered from the reaction mixture by simple filtration and…
A DFT study of the Diels–Alder reaction between methyl acrolein derivatives and cyclopentadiene. Understanding the effects of Lewis acids catalysts b…
2006
Abstract The effects of Lewis acid catalysts based on sulfur containing boron heterocycles on the Diels–Alder reactions of two methyl acroleins with cyclopentadiene have been studied using DFT methods. These reactions take place along highly asynchronous concerted processes. While the reaction with crotonaldehyde leads to the expected endo adduct, the reaction with methacrolein leads to exo one in agreement with the experiments. The catalytic effect can be explained through the analysis of the electrophilicity index (ω) of the reagents, and the molecular structure of the corresponding transition structures.
Iron(iii) oxamato-catalyzed epoxidation of alkenes by dioxygen and pivalaldehyde
1997
A new iron(III)–carbonato monomeric complex of orthophenylenebis( oxamato) (opba) 1 is synthesized, and spectroscopically and structurally characterized; it is a moderately efficient non-heme catalyst for the aerobic epoxidation of alkenes with co-oxidation of pivalaldehyde. Ruiz Garcia, Rafael, Rafael.Ruiz@uv.es ; Fernandez Picot, Isabel, Isabel.Fernandez@uv.es ; Pedro Llinares, Jose Ramon, Jose.R.Pedro@uv.es
The role of H2O in the photocatalytic oxidation of toluene in vapour phase on anatase TiO2 catalyst
1999
Abstract Photocatalytic oxidation of toluene has been carried out in a gas–solid regime by using polycrystalline anatase TiO2 in a fixed-bed continuous reactor. Air containing toluene and water vapours in various molar ratios was fed to the photoreactor irradiated by a medium pressure Hg lamp. Toluene was mainly photo-oxidised to benzaldehyde, and small amount of benzene, benzyl alcohol and traces of benzoic acid and phenol were also detected. In the presence of water, no decrease of photoreactivity was observed at steady-state conditions. By removing water vapour from the feed, the conversion of toluene to benzaldehyde was almost completely inhibited, and an irreversible deactivation of th…
Association of military training with oxidative stress and overreaching.
2011
ABSTRACT: We hypothesized that increased oxidative stress and disrupted redox balance may be predisposing factors and markers for overreaching (OR). Purpose: The study's purpose was to examine whether oxidative stress markers and antioxidant status and physical fitness are related to OR during an 8-wk military basic training (BT) period. Methods: Oxidative stress and antioxidant status were evaluated in the beginning and after 4 and 7 wk of training in 35 males (age = 19.7 ± 0.3 yr) at rest and immediately after a 45-min submaximal exercise. Physical activity (PA) was monitored by an accelerometer throughout BT. Indicators of OR were also examined. Results: From baseline to week 4, increase…
Oxidative Dehydrogenation of Ethanol on Gold : Combination of Kinetic Experiments and Computation Approach to Unravel the Reaction Mechanism
2021
Abstract Selective alcohol dehydrogenation on heterogeneous catalysts is a key industrial reaction for production of aldehydes, ketones, and carboxylic compounds. Design of catalysts with improved activity and selectivity requires understanding of the reaction mechanism and kinetics. Herein, experiments, density functional theory (DFT) and kinetic modelling were combined to elucidate the mechanism and kinetics of ethanol oxidative dehydrogenation to acetaldehyde on gold catalysts. Catalytic experiments clearly emphasized the role of oxygen in this reaction. Ethanol conversion was rather independent on the gold cluster size. Formation of minor products, acetic acid and ethyl acetate was stru…
Stereoselective Synthesis of Spiro-Decalin Oxindole Derivatives via Sequential Organocatalytic Michael-Domino Michael/Aldol Reaction.
2022
A highly stereoselective procedure for the synthesis of spiro-polycyclic oxindoles bearing five contiguous stereogenic centers including two tetrasubstituted carbons has been developed. Under sequential organocatalysis performed by a pyrrolidine-based organocatalyst and DBU, a highly atom-economical Michael–domino Michael/aldol reaction sequence was optimized, yielding variously functionalized spiro-decalin oxindoles with excellent stereoselectivity (>99:1 dr, up to 92% ee). peerReviewed
A fast and simple spectrofluorometric method for the determination of alendronate sodium in pharmaceuticals
2014
Introduction: Alendronate sodium enhances bone formation and increases osteoblast proliferation and maturation and leads to the inhibition of osteoblast apoptosis. Therefore, a rapid and simple spectrofluorometric method has been developed and validated for the quantitative determination of it. Methods: The procedure is based on the reaction of primary amino group of alendronate with o-phthalaldehyde (OPA) in sodium hydroxide solution. Results: The calibration graph was linear over the concentration range of 0.0-2.4 μM and limit of detection and limit of quantification of the method was 8.89 and 29 nanomolar, respectively. The enthalpy and entropy of the reaction between alendronate sodium …
Changes in Oxidative Stress Index and Lipid Peroxidation Product in the Brain of Rats with Lesion of Central Dopaminergic System after Propofol Admin…
2019
Propofol is a commonly used intravenous anesthetic agent with antioxidant properties. However, the effect of propofol on oxidative stress index (OSI) and lipid peroxidation in Parkinson’s disease is still unknown. The present study aimed to evaluate the effect of propofol on OSI and malondialdehyde (MDA) level in the selected brain regions of the rats with Parkinson’s disease (PD). 32 male Wistar rats were divided into four groups: I- control group, II- group with PD, III-control group with propofol, IV-PD group with propofol. 60mg/kg of propofol was given to the 8-weeks-old rats intraperitoneally, and the selected parts of the rats’ brains (frontal cortex, striatum, thalamus and hippocampu…
Changes in Oxidative Stress Index and Lipid Peroxidation Product in the Brain of Rats with Lesion of Central Dopaminergic System after Propofol Admin…
2019
Propofol is a commonly used intravenous anesthetic agent with antioxidant properties. However, the effect of propofol on oxidative stress index (OSI) and lipid peroxidation in Parkinson’s disease is still unknown. The present study aimed to evaluate the effect of propofol on OSI and malondialdehyde (MDA) level in the selected brain regions of the rats with Parkinson’s disease (PD). 32 male Wistar rats were divided into four groups: I- control group, II- group with PD, III-control group with propofol, IV-PD group with propofol. 60mg/kg of propofol was given to the 8-weeks-old rats intraperitoneally, and the selected parts of the rats’ brains (frontal cortex, striatum, thalamus and hippocampu…