Showing papers on "Benzaldehyde published in 2001"
TL;DR: The alcohol group of hydroxymethylfurfural (compound 1, HMF) is preferentially oxidized by dioxygen and metal/bromide catalysts [Co/Mn/Br, Co/mn=Br/(Co+Mn) = 1.0 mol/mol] to form the dialdehyde, 2,5-diformylfuran (DFF) in 57% isolated yield as mentioned in this paper.
Abstract: The alcohol group of hydroxymethylfurfural (compound 1, HMF) is preferentially oxidized by dioxygen and metal/bromide catalysts [Co/Mn/Br, Co/Mn/Zr/Br; Co/Mn=Br/(Co+Mn) = 1.0 mol/mol] to form the dialdehyde, 2,5-diformylfuran (compound 2, DFF) in 57% isolated yield. HMF can be also oxidized, via a network of identified intermediates, to the highly insoluble 2,5-furandicarboxylic acid (compound 5, FDA) in 60% yield. For comparison, benzyl alcohol gives benzaldehyde in 80% using the same catalyst system. Over-oxidation (to CO2) of HMF is much higher than that of the benzyl alcohol but can be greatly reduced by increasing catalyst concentration.
337 citations
TL;DR: In this paper, thermal and hydrothermal treatments have been applied to an amorphous TiO2 precursor for obtaining nanosized TiO 2 particles (P11t and P11h, respectively) of different photocatalytic properties.
327 citations
TL;DR: In this paper, Pd catalysts on different supports (active carbon, silica, alumina) were studied for the selective hydrogenation of benzaldehyde to benzyl alcohol, and they were characterized by TPR, CO chemisorption and XRD.
Abstract: Pd catalysts on different supports (active carbon, silica, alumina) were studied for the selective hydrogenation of benzaldehyde to benzyl alcohol. They were characterized by TPR, CO chemisorption and XRD. Batch hydrogenation tests were performed before and after sulfur poisoning. Strong metal–support interaction was found for Pd/alumina, giving high Pd dispersion. Chemisorption stoichiometry Pd/CO=2 was confirmed again. While Pd/C has the highest activity for benzaldehyde hydrogenation, a satisfactory selectivity to benzyl alcohol requires an oxidic carrier or proper sulfur poisoning of Pd/C.
118 citations
TL;DR: Salen-type Schiff base ligands incorporating two different benzylidene moieties and a diamine backbone were synthesized in high yield (80-90%) under mild conditions via a stepwise approach as discussed by the authors.
117 citations
TL;DR: In this paper, a highly active solid superacid of sulfated tin oxide was prepared from tin oxide gel, which was precipitated by the hydrolysis of SnCl4 and washed with ammonium acetate solution, followed by exposure to aqueous sulfuric acid and calcining.
Abstract: A highly active solid superacid of sulfated tin oxide was prepared from tin oxide gel, which was precipitated by the hydrolysis of SnCl4 and washed with aqueous ammonium acetate solution, followed by exposure to aqueous sulfuric acid and calcining. Differencial thermal analysis suggested that the acetate ion remaining on the surface was replaced with sulfate ion. The acid strength of the sulfated tin oxide estimated by temperature-programmed desorption using argon was higher than that of sulfated zirconia, a well-known solid superacid, the activation energy of Ar desorption by the former being 10.6 kJ mol-1 in comparison with 9.3 kJ mol-1 by the latter. The sulfated tin oxide showed activities much higher than those of the sulfated zirconia for the skeletal isomerization of n-pentane, the Mukaiyama aldol condensation of 1-trimethylsilyloxy-1-cyclohexene with benzaldehyde, and the benzoylation of toluene with benzoic anhydride.
117 citations
TL;DR: The formation of benzoin (Ph-CHOH-CO-Ph) from two molecules of benzaldehyde, catalyzed by 3-benzyl-5-(2-hydroxyethyl)-4-methylthiazolium bromide in methanol buffered with Et(3)N/Et( 3)NH(+)Cl(-) has been studied.
Abstract: The formation of benzoin (Ph-CHOH-CO-Ph) from two molecules of benzaldehyde, catalyzed by 3-benzyl-5-(2-hydroxyethyl)-4-methylthiazolium bromide in methanol buffered with Et3N/Et3NH+Cl- has been studied. Initial-rate studies at various concentrations of PhCHO (0.1−1.7 M) showed that the reaction is close to being first order in PhCHO. Following the reaction in deuteriomethanol, 1H NMR spectroscopy allowed rate constants for all three kinetically significant steps to be determined. These show that all three steps are partially rate-determining. A normal deuterium kinetic isotope effect for the overall reaction (kH/kD ≈ 3.4) is observed using PhCDO, and a large inverse solvent isotope effect (kD/kH ≈ 5.9) is observed using deuteriomethanol, consistent with the kinetic scheme presented here.
105 citations
TL;DR: Optically active aminonaphthol 3 obtained by condensation of 2-naphthols, benzaldehyde, and (S)-methylbenzylamine followed by N-methylation was found to catalyze the enantioselective ethylation of aryl aldehydes to secondary alcohols with high enantiOSElectivities at room temperature.
95 citations
TL;DR: In this paper, the selectivity of benzyl alcohol to benzaldehyde was investigated over pumice supported bimetallic and monometallic Pd and Ag catalysts, and the results indicated that Ag 0 and Pd 0 were the catalytic sites acting with certain synergism.
84 citations
TL;DR: The addition of a β C-H bond to the formyl group of aldehydes to olefins with the aid of Ru(H)2(CO)(PPh3)3 as a catalyst was reported in this article.
Abstract: The addition of a β C–H bond to the formyl group of aldehydes to olefins took place with the aid of Ru(H)2(CO)(PPh3)3 as a catalyst. Several olefins can be used in the catalytic reaction of conjugate enals. The presence of a sterically hindered substituent at the ortho position of benzaldehyde and the presence of an electron donating substituent appear to be important factor in accomplishing the desired coupling reaction.
82 citations
TL;DR: In this article, the use of N2O5 and a Fe(III) catalyst for the nitration of aromatic rings is described, which is compatible with most functional groups and results in near quantitative yields in 4 min.
73 citations
TL;DR: Temperature-programmed hydrogenation (TPH) is shown to be an effective technique to characterize toluene intermediates as discussed by the authors, where Titania is a hydrogenation catalyst at elevated temperatures, and the intermediates hydrogenate to benzene, which are more weakly bound.
TL;DR: In this article, the use of heteropolyacids in conjunction with phase transfer catalysts in the oxidation of benzyl alcohol to benzaldehyde with hydrogen peroxide as the oxidising agent has been investigated.
Abstract: The use of heteropolyacids in conjunction with phase transfer catalysts in the oxidation of benzyl alcohol to benzaldehyde with hydrogen peroxide as the oxidising agent has been investigated. The effect of various parameters on the conversion of benzyl alcohol was studied including the effect of the nature of the heteropolyanion as well as the effect of the partial substitution of protons in the heteropolyacid. Surfactant-type phase transfer catalysts were found to display high catalytic activity with cetyltrimethylammonium bromide (CTMAB) being the most effective phase transfer catalyst among those examined. A suitable mechanism for this reaction has been proposed and a kinetic model has been developed in order to explain the observed experimental results.
TL;DR: Palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate with a dimethyl malonate-BSA-LiOAc system and its derivatives has been successfully carried out in the presence of a new chiral hydrazone ligands in high yields with high enantioselectives.
Abstract: Palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate (4) with a dimethyl malonate−BSA−LiOAc system and its derivatives has been successfully carried out in the presence of a new chiral hydrazone ligands such as 2-(diphenylphosphino)benzaldehyde SAMP hydrazone (DPPBA-SAMP) (3a) in high yields with high enantioselectives.
TL;DR: A monomeric titanocene(III) derivative, Cp(2)TiPh, effectively promoted the pinacol coupling of both an aromatic aldehyde, benzaldehyde, and an aliphatic alde Hyde, 3-phenylpropionaldehyde, and was successfully generated by a catalytic amount of a precursor and its stoichiometric amount of Zn.
Abstract: A monomeric titanocene(III) derivative, Cp2TiPh, effectively promoted the pinacol coupling of both an aromatic aldehyde, benzaldehyde, and an aliphatic aldehyde, 3-phenylpropionaldehyde. The same reactive complex was successfully generated by a catalytic amount of a precursor, Cp2Ti(Ph)Cl, and its stoichiometric amount of Zn. The Cp2TiPh-catalyzed pinacol coupling of benzaldehyde derivatives and aliphatic aldehydes afforded the corresponding 1,2-diols in high yields with moderate to good threo-selectivity. On the other hand, Cp2TiPh-catalyzed pinacol cyclization of dials gave cyclic 1,2-diols with excellent diastereoselectivity. The extension of this protocol to chiral dials demonstrated that the phenyltitanium complex catalytically transmitted an axial chirality or a central chirality of the starting dials to the central chirality of the resultant 1,2-diols.
TL;DR: In this article, the reaction of dioxygen with the copper(I) Bz3tren complex was investigated using low temperature stopped-flow techniques, and the formation of a superoxo as well as a peroxo complex as intermediates was detected spectroscopically.
TL;DR: In this paper, the reaction kinetics of the laccase-mediator system (LMS) have been investigated by means of a model reaction, the oxidation of 2,4-dimethoxybenzyl alcohol (DMBA, 1) to 2, 4-dimethylbenzaldehyde (DMA, 2).
Abstract: Investigations into the reaction kinetics of the laccase-mediator system (LMS) have been carried out. Two widely used mediators, 2,2'-azino-bis(3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS, 3) and 1-hydroxybenzotriazole (HOBT, 4), were compared by means of a model reaction, the oxidation of 2,4-dimethoxybenzyl alcohol (DMBA, 1) to 2,4-dimethoxybenzaldehyde (DMA, 2). The consumption of dioxygen was recorded electrochemically, substrate consumption and product formation were monitored by GLC. With ABTS as the mediator, the LMS reaction proceeded in two clearly distinguishable stages. The first phase is characterized by a fast decrease in oxygen with zero-order kinetics and no detectable formation of 2,4-dimethoxybenzaldehyde (2). ABTS is converted into oxidized species, the cation radical 6 and the dication 7, respectively. In the second phase, oxygen consumption was considerably slower and followed a second-order kinetics, while the benzaldehyde was produced according to a zero-order rate law. According to the kinetic studies, the ABTS dication, but not the enzyme itself, is acting as the actual oxidant. The rate of oxidation product formation increased with increasing mediator / benzyl alcohol ratio. Less oxygen than the equivalent amount was consumed in the second reaction stage indicating that the oxidized ABTS formed in the first stage acts as an oxidant reservoir, being reduced to ABTS in turn. The LMS reaction with HOBT (4) as the mediator did not exhibit distinguishable phases, and was characterized by a comparatively slow oxygen uptake with zero-order kinetics throughout. Enzymatic oxidation of HOBT to the HOBT radical (5), which acts as the actual oxidant towards the benzyl alcohol, was the rate-determining step. The production of 2,4-dimethoxybenzaldehyde thus followed a zero-order rate law as well. The reaction rate increased with increasing HOBT / benzyl alcohol ratios. Increasing concentrations of 4 caused less oxygen to be consumed per equivalent of benzaldehyde formed, indicating the occurrence of another reaction pathway at high mediator charges. At low HOBT / benzyl alcohol ratios the HOBT radical (5) acts as one-electron oxidant and is reduced to HOBT in a reversible process. In contrast, at higher HOBT / benzyl alcohol ratios 5 acts as a three-electron oxidant, being irreversibly reduced to benzotriazole. At commonly employed mediator concentrations, a superposition of both mechanisms results. The pure borderline cases can only be observed at HOBT / benzyl alcohol ratios below 1 and above 6, respectively.
TL;DR: In this article, the authors used a duo-trio test to compare three labelled analogues of benzaldehyde; 13 C 6 (ring)-benzaldehyde, 13 CHO-Benzaldehyde and benzaldehyde-d 6, and found a statistically significant difference in odour perception relative to the unlabeled benzaldehyde.
TL;DR: In this article, a series of chiral β-amino alcohols were obtained by the reaction of secondary amines with a 1:1 mixture of cis- and trans-limonene oxide in the presence of water as a catalyst.
TL;DR: In this article, the synthesis of a soluble polymer containing BINOL residues is described, and a Titanium-BINOLate and AlLibis(binaphthoxide) catalysts are easily generated from this polymer and applied to the asymmetric reaction of Et2Zn with benzaldehyde and the inverse Michael addition, respectively.
Abstract: The synthesis of a soluble polymer containing BINOL residues is described. Titanium-BINOLate and AlLibis(binaphthoxide) catalysts are easily generated from this polymer and applied to the asymmetric reaction of Et2Zn with benzaldehyde and the asymmetric Michael addition, respectively. The products are obtained in good yields with high enantioselectivities.
TL;DR: In this paper, the authors found that CuAPO-5 was an efficient catalyst in hydroxylation of alkyl-substituted benzenes, and that MCM-41 was an effective catalyst in catalyzing the oxidation of trimethylphenol to trimethylbenzoquinone at mild reaction conditions.
TL;DR: In this article, the success of dipyrromethanecarbinols in rational routes to porphyrinic macrocycles requires catalysis conditions that enable irreversible condensation, thereby avoiding substituent scrambling and formation of undesired porphrin products.
Abstract: The successful use of dipyrromethanecarbinols in rational routes to porphyrinic macrocycles requires catalysis conditions that enable irreversible condensation, thereby avoiding substituent scrambling and formation of undesired porphyrin products. Previously, successful conditions of trifluoroacetic acid (TFA) (30 mM) in acetonitrile were identified following a lengthy survey of TFA and BF3-etherate catalysis in diverse solvents. In this study, focus was placed on the acid catalyst by examining 17 acids in CH2Cl2, the traditional solvent for two-step, one-flask porphyrin syntheses. In the self-condensation of the carbinol derived from 1-(4-methylbenzoyl)-5-phenyldipyrromethane, porphyrin yields of 9–55% were obtained from the various acids, compared to 20% under TFA catalysis in acetonitrile. A number of catalytic conditions that produce little to no porphyrin in reactions of pyrrole + benzaldehyde afforded good yields of porphyrin and the suppression of scrambling in reactions of dipyrromethanecarbinols....
TL;DR: Magnesium monoperoxyphthalate and urea-hydrogen peroxide-acetic anhydride are effective reagents in the oxidation of benzaldehyde to benzoic acid and o- and p-methoxybenzaldehyde to the corresponding phenols as discussed by the authors.
TL;DR: In this article, resorcinol and benzaldehyde derivatives are prepared in polypropylene glycol, which is readily recycled, and the solvent-free method measures up well with respect to energy usage, solvent wastes and associated hazards, reaction time and yield.
TL;DR: The formation of adducts involving the bidentate Lewis acid 1,2-bis(chloromercurio)tetrafluorobenzene (1) and small electron rich organic molecules has been investigated.
TL;DR: The Meerwein-Ponndorf-Verley reaction of benzaldehyde with ethanol in the liquid phase in the presence of basic catalysts consisting of magnesium oxide, calcium oxide, and mixed oxides, was studied.
TL;DR: In this article, phenylalanine (Phe) was oxidized with either potassium peroxodisulfate or glyoxal, and sixteen volatile compounds having their origin in the amino acid molecule were detected and identified.
Abstract: Phenylalanine (Phe) was oxidized with either potassium peroxodisulfate or glyoxal. Volatile reaction products were isolated and analyzed by GC/FID and GC/MS. Nonvolatile products were derivatized with diazomethane and analyzed by the same methods. Under the experimental reaction conditions (equimolar ratio of reactants, 100 °C, 1 h), the decomposed amount of amino acid was 28% (glyoxal) and to 74% (peroxodisulfate), respectively. Sixteen volatile compounds having their origin in the amino acid molecule were detected and identified. The major compound was phenylacetaldehyde (208 mg/peroxodisulfate, 11 mg/glyoxal), followed by bibenzyl, benzaldehyde, and benzyl alcohol. Other products were present in concentrations lower then 0.1 mg. For comparison, the lower homologue of Phe, phenylglycine, was oxidized under the same conditions. Analogously, 21% (glyoxal) and 65% (peroxodisulfate) of this amino acid decomposed, predominantly to benzaldehyde (242 mg/peroxodisulfate, 95 mg/glyoxal). A minor decomposition product was benzoic acid (2.9 mg), other ten products arose at levels lower then 0.1 mg. The formation of minor oxidation products during Strecker degradation of amino acids suggests the importance of radical reactions. In systems comprising glyoxal, ten heterocyclic compounds arose as minor products (3-furancarbaldehyde, 5-methyl-2-furancarbaldehyde, 2-pyrrolcarbaldehyde, 3-phenylpyridine, pyrazine, methyl-, ethyl-, vinyl-, and 2-phenylethylpyrazine).
TL;DR: 3-Ethyl-5,10,15,20,20-tetraphenyl-2-aza-21-carbaporphyrin is the major macrocyclic product in the condensation of 2-ethylpyrrole, pyrrole and benzaldehyde as mentioned in this paper.
TL;DR: In this article, Niobium chloride was used to promote the addition of allylstannanes to aromatic and aliphatic aldehydes, and excellent syn diastereoselectivity was obtained.
TL;DR: In this article, the synthesis of 2-phenyl-3-aminopyridine from 2-chloro-3 -amino acid was described using an imine as a protecting group.