Showing papers on "Benzaldehyde published in 2005"

Hydroacylation of 2-vinyl benzaldehyde systems: an efficient method for the synthesis of chiral 3-substituted indanones.

Abstract: Asymmetric rhodium-catalyzed hydroacylation has been utilized in the synthesis of 3-substituted indanones with high conversions and enantioselectivity. The hydroacylation reaction of 2-vinyl benzaldehyde had been previously reported to give a low yield of indanone and an unidentified product. We have identified this compound as a dimer of the starting material. Substitution at the α-position of the 2-vinyl benzaldehyde substrates blocks the competitive dimerization reaction and allows the reaction to proceed with yields generally greater than 90%. Utilization of BINAP as a chiral ligand results in good chemical yields and enantioselectivity greater than 95% in most cases.

Unraveling the surface reactions during liquid-phase oxidation of benzyl alcohol on Pd/Al2O3: An in situ ATR-IR study

Abstract: The palladium-catalyzed liquid-phase reaction of benzyl alcohol to benzaldehyde was investigated in the presence and absence of oxygen by attenuated total reflection infrared (ATR−IR) spectroscopy. The 5 wt % Pd/Al2O3 catalyst was fixed in a flow-through ATR−IR cell serving as a continuous-flow reactor. The reaction conditions (cyclohexane solvent, 323 K, 1 bar) were set in the range commonly applied in the heterogeneous catalytic aerobic oxidation of alcohols. The in situ ATR−IR study of the solid−liquid interface revealed a complex reaction network, including dehydrogenation of benzyl alcohol to benzaldehyde, decarbonylation of benzaldehyde, oxidation of hydrogen and CO on Pd, and formation of benzoic acid catalyzed by both Pd and Al2O3. Continuous formation of CO and its oxidative removal by air resulted in significant steady-state CO coverage of Pd during oxidation of benzyl alcohol. Unexpectedly, benzoic acid formed already in the early stage of the reaction and adsorbed strongly (irreversibly) on th...

Selective liquid phase oxidation of toluene with air

Abstract: Catalysis of simple cobalt tetraphenylporphyrin for selective liquid phase oxidation of toluene with air is first reported. By the catalysis of simple cobalt tetraphenylporphyrin, the selective oxidation of toluene with air in the absence of any solvents or promoters will produce benzaldehyde and benzyl alcohol. Compared with the present synthetic method of benzaldehyde and benzyl alcohol by the chlorination of toluene followed by hydrolysis, which has been used in the world industry, the new method has the advantage of friendly environmental effects. The researchers found that the reaction time, temperature, air pressure, the amount of catalyst and the flow rates of air influenced the toluene conversion and the selectivity of benzaldehyde and benzyl alcohol. By the use of 3.2 × 10 −5 M cobalt tetraphenylporphyrin as catalyst, toluene oxidation with air under the optimum conditions of 160 °C and 0.8 MPa and 0.04 m 3 /h airflow produced benzaldehyde and benzyl alcohol at 60% selectivity and 8.9% conversion of toluene. The mole turnover numbers of the catalyst was about 25,000. A possible mechanism is also suggested.

Dual Lewis Acid−Lewis Base Activation in Enantioselective Cyanation of Aldehydes Using Acetyl Cyanide and Cyanoformate as Cyanide Sources

Abstract: Dual activation by a chiral Lewis acid and an achiral or chiral Lewis base enabled cyanation of both aromatic and aliphatic aldehydes with acetyl cyanide and ethyl cyanoformate to provide direct access to O-acetylated and O-alkoxycarbonylated cyanohydrins, respectively, under mild conditions. With a combination of a Ti−salen catalyst and Et3N, benzaldehyde was converted to the O-acetylated cyanohydrin with 94% ee within 10 h at −40 °C in 89% isolated yield.

Liquid Phase Oxidation of Toluene to Benzaldehyde with Molecular Oxygen over Copper-Based Heterogeneous Catalysts

Abstract: We conducted the liquid phase oxidation of toluene with molecular oxygen over heterogeneous catalysts of copper-based binary metal oxides. Among the copper-based binary metaloxides, iron-copper bi- nary oxide (Fe/Cu ¼ 0.3 atomic ratio) was found to be the best catalyst. In the presence of pyridine, overox- idation of benzaldehyde to benzoic acid was partially prevented. As a result, highly selective formation of benzaldehyde (86% selectivity) was observed after 2 h of reaction (7% conversion of toluene) at 463 K and 1.0 MPa of oxygen atmosphere in the presence of pyridine. These catalytic performances were similar or better than those in the gas phase oxidation of tol- uene at reaction temperatures higher than 473 K and under 0.5 - 2.5 MPa. It was suggested from competi- tive adsorption measurements that pyridine could re- duce the adsorption of benzaldehyde. At a long reac- tion time of 4 h, the conversion increased to 25% and benzoic acid became the predominant reaction prod- uct (72% selectivity) in the absence of pyridine. The yield of benzoic acid was higher than that in the Snia-Viscosa process, which requires corrosive halo- gen ions and acidic solvents in the homogeneous reac- tion media. The catalyst was easily recycled by simple filtration and reusable after washing and drying.

A simple chemical synthesis of nanocrystalline AFe2O4 (A = Fe, Ni, Zn): An efficient catalyst for selective oxidation of styrene

Abstract: Nanosized spinel ferrite (AFe2O4, A = Ni, Fe, Zn) catalysts are prepared by ‘bottom-up’ approach, i.e. first forming the nanostructured building blocks and then assembling them into the final material with average particle size of 7–12 nm and surface area of 80–100 m2/g. The synthesized nanocrystallites were characterized by thermal analysis, powder X-ray diffraction, transmission electron microscopy and inductively coupled plasma (atomic emission spectroscopy) technique for evaluating phase, structure and morphology and stoichiometry. These materials were found to be very good catalysts for the oxidation of styrene to benzaldehyde in the presence of hydrogen peroxide. Of the several catalysts tried, magnetite (Fe3O4) has shown to have the best catalytic activity for the above reaction. The effects of solvent medium used, styrene:hydrogen peroxide molar ratio, reaction temperature, time and reaction atmosphere required for the complete conversion of styrene to benzaldehyde were also studied. Based on our findings, a plausible mechanism involved in the catalytic reaction is proposed.

Photochemical reaction mechanisms of 2-nitrobenzyl compounds: 2-nitrobenzyl alcohols form 2-nitroso hydrates by dual proton transfer.

Abstract: Irradiation of 2-nitrobenzyl alcohol (1, R = H) and 1-(2-nitrophenyl)ethanol (1, R = Me) in various solvents yields 2-nitroso benzaldehyde (4, R = H) and 2-nitroso acetophenone (4, R = Me), respectively, with quantum yields of about 60%. The mechanism of this reaction, known since 1918, was investigated using laser flash photolysis, time-resolved infrared spectroscopy (TRIR), and 18O-labeling experiments. The primary aci-nitro photoproducts 2 react by two competing paths. The balance between the two depends on the reaction medium. Reaction via hydrated nitroso compounds 3 formed by proton transfer prevails in aprotic solvents and in aqueous acid and base. In water, pH 3–8, the classical mechanism of cyclization to benzisoxazolidine intermediates 5, followed by ring opening to carbonyl hydrates 6, predominates. The transient intermediates 3 and 6 were identified by TRIR. Potential energy surfaces for these reactions were mapped by density functional calculations.

Nickel containing Mg-Al hydrotalcite-type anionic clay catalyst for the oxidation of alcohols with molecular oxygen

Abstract: Nickel(II) containing magnesium-aluminum (3/1) hydrotalcite(HT)-type anionic clays have been prepared by co-precipitation and tested for a catalyst for liquid-phase oxidation of alcohols with molecular oxygen. The Ni substitution for the Mg site in Mg3Al HT resulted in an appearance of the catalytic activity and the composition of Mg2.5Ni0.5Al HT was the most effective. The oxidation of primary and secondary alcohols afforded the corresponding carbonyl compounds mainly; benzyl alcohol was the most efficiently oxidized to benzaldehyde. The yield of benzaldehyde over the hydrotalcite catalyst increased significantly with increasing nickel content up to ca. 7.6 wt%, where atomically isolated and octahedrally coordinated Ni(II) sites was effective for the oxidation with molecular oxygen. Use of non-polar solvents, such as hexane, cyclohexane, and toluene, was favorable for the oxidation reaction, among which toluene afforded the highest yield of benzaldehyde. The octahedrally coordinated Ni(II) cations incorporated inside the framework of hydrotalcite do not leach during the reaction and worked as a heterogeneous catalyst. It is considered that the Ni(II) site worked as the active site by activating molecular oxygen assisted by the Mg(II) as a base and simultaneously alcohol was activated by the Al(III) as an acid, resulting in an enhancement of the activity of the Mg2.5Ni0.5Al HT heterogeneous catalyst for alcohol oxidation.

Pd(II)-biquinoline catalyzed aerobic oxidation of alcohols in water

Abstract: An aqueous palladium catalyst that is stabilized by a water-soluble biquinoline-based ligand was employed for the aerobic oxidation of secondary and primary alcohols. Secondary alcohols afforded the corresponding ketones in high yield with selectivities greater than 90%. Aliphatic primary alcohols were fully oxidized to carboxylic acid products under the same reaction conditions, with various amounts of ester byproduct. Benzyl alcohol can be converted to a mixture of benzaldehyde and benzoic acid, where the relative amounts are dependent on the reaction conditions, while substituted benzylic alcohols gave primarily benzaldehyde derivatives. In contrast to related systems, the catalyst used in this study is tolerant of additional coordinating groups on the benzyl alcohol substrate. In all examples of alcohol oxidation, water is used as the only reaction solvent and air is used as the oxidant, thus these conversions could serve as environmentally benign “green” alternatives to traditional oxidation methods.

Hydrogenation of benzaldehyde and cinnamaldehyde in compressed CO2 medium with a Pt/C catalyst: a study on molecular interactions and pressure effects.

Abstract: The hydrogenation of benzaldehyde and cinnamaldehyde has been studied with a 5% Pt/C catalyst in compressed CO2. The effect of CO2 pressure on the total conversion was found to be different between the two aldehydes. The total conversion of benzaldehyde merely decreases with increasing CO2 pressure, while that of cinnamaldehyde shows a maximum at a certain pressure. High-pressure FTIR measurements indicate the existence of interactions of CO2 with the aldehydes. The absorption of ν(CO) red-shifts at increasing CO2 pressure, and this red-shift is more significant for cinnamaldehyde than for benzaldehyde, indicating that the CO bond of the former becomes more reactive than the latter. The difference in the mode of interactions of CO2 with these aldehydes has also been indicated by changes of ν(CO) of CO2. Thus, the conversion of benzaldehyde will decrease with increasing CO2 pressure because of a simple dilution by introducing a larger quantity of CO2. For cinnamaldehyde, the conversion will increase at low...

Catalyzed asymmetric aryl transfer reactions to aldehydes with boroxines as aryl source

Abstract: Asymmetric aryl transfer of triphenylboroxin to a set of aryl aldehydes has been carried out in the presence of chiral amino alcohols derived from ( S )-proline with high enantioselectivity. Substituted phenyl boroxins were also used as aryl source in asymmetric arylation of benzaldehyde.

Polycondensation product based on aromatic or heteroaromatic compounds, method for the production thereof, and use thereof

Abstract: Disclosed is a polycondensation product comprising A) an aromatic or heteroaromatic compound containing 5 to 10 C atoms or heteroatoms, said compound being provided with an average of 1 to 300 oxyethylene groups and/or oxypropylene groups per molecule which are linked to the aromatic or heteroaromatic compound via an O atom or N atom, and optionally B) an aromatic compound selected among the group comprising phenols, phenol ether, naphthols, naphthol ether, anilines, furfuryl alcohols, and/or an aminoplast former selected among the group comprising melamine (derivatives), urea (derivatives), and carboxylic acid amides, and C) an aldehyde selected among the group comprising formaldehyde, glyoxylic acid, and benzaldehyde or mixtures thereof, the benzaldehyde optionally containing acid groups in the form of COOMa, SO3Ma, and PO3Ma, wherein M = H, akali metal or alkaline earth metal, ammonium, or organic amine radicals and a = 1/2, 1, or 2. Surprisingly, the inventive polycondensation product causes very good liquefaction of hydraulic binding agents, e.g. cement, resulting in substantially improved liquefaction of the construction material at a lower dose while pourability can be maintained over a longer period of time as opposed to naphthalene sulfonates or melamine sulfonates.

Synthesis, characterization and catalytic potentials of polymer anchored copper(II), oxovanadium(IV) and dioxomolybdenum(VI) complexes of 2-(α-hydroxymethyl)benzimidazole

Abstract: 2-(α-Hydroxymethyl)benzimidazole (Hhmbmz) has been covalently anchored to chloromethylated polystyrene cross-linked with 5% divinylbenzene. This chelating resin reacts with cupric acetate, vanadyl sulphate and [MoO 2 (acac) 2 ] (Hacac = acetylacetone) in presence of Hhmbmz to give complexes PS-[Cu(hmbmz) 2 ], PS-[VO(hmbmz) 2 ] and PS-[MoO 2 (hmbmz) 2 ] (where, PS-hmbmz = deprotonated 2-(α-hydroxymethyl) benzimidazole covalently linked with polymer), respectively. These complexes were characterized by elemental analyses, FT-IR, EPR and electronic spectra, SEM and TGA-DTA methods. EPR results indicate that complexes are well dispersed in the polymeric support. Complexes PS-[Cu(hmbmz) 2 ] and PS-[VO(hmbmz) 2 ] have been used as catalysts for the oxidation of styrene and ethyl benzene while PS-[VO(hmbmz) 2 ] and PS-[MoO 2 (hmbmz) 2 ] for the oxidative bromination of salicylaldehyde. Oxidation of styrene gives three major products, styrene oxide, benzaldehyde and benzoic acid while ethyl benzene gives acetophenone as the major product. Oxidative bromination of salicylaldehyde using H 2 O 2 /KBr gives 5-bromosalicylaldehyde selectively in quantitative yield. EPR spectra of both freshly prepared and recovered catalysts are identical, which indicate that the metal-Schiff base moiety is intact and the coordination environments are not altered during the reaction.

Kinetics of oxidation of benzyl alcohol with dilute nitric acid

Abstract: The oxidation of benzyl alcohol by dilute nitric acid has been selected for the study as a typical method for the manufacture of industrially important intermediate benzaldehyde. All the reactions ...

An efficient procedure for protection of carbonyls catalyzed by sulfamic acid

Abstract: Sulfamic acid (H2NSO3H) has been used as an efficient and recyclable catalyst for acetalization and ketalization between carbonyl compounds and diols. This system is reasonably general and can be applied to converting several carbonyl compounds to the corresponding acetals and ketals using neopentyl glycol and other diols as protection reagents. The use of an inexpensive, green and stable catalyst, convenient reaction operation and high selectivity to desired products are the features contained in this reaction. Sulfamic acid can be reused five times in the reaction between benzaldehyde and neopentyl glycol without loss of activity.

Biotransformation of benzaldehyde-type and acetophenone-type derivatives by Pharbitis nil hairy roots.

Abstract: The glucosylation of some coumarin and flavone derivatives on incubation with the hairy roots of morning glory (Pharbitis nil) was previously reported. We further studied the biotransformation of benzaldehyde- and acetophenone-type derivatives. Vanillin and isovanillin were reduced to alcoholic derivatives and glucosylated at the phenolic and the alcoholic hydroxyl groups. In the case of 3,4-dihydroxybenzaldehyde, the formyl group was reduced and the 3-hydroxyl or 4-hydroxyl groups were glucosylated to give monoglucosides. The 3-hydroxyl group was predominantly glucosylated to the 4-hydroxyl group. 4-β-D-Glucopyranosyloxy-3-methoxybenzylalcohol was obtained in low yield. In time-course experiments with vanillin, it was found that the high-level reduction of the formyl group and glucosylation of the phenolic hydroxyl group occurred, and finally 4-O-β-D-glucopyranosylvanillylalcohol was obtained as the main product. In the case of 3,4-dimethoxybenzaldehyde, 3,4,5-trimethoxybenzaldehyde, and salicylaldehyde, the formyl groups were reduced, and then the hydroxyl groups at the benyl position were glucosylated to give alcoholic glucosides in relatively high yields. In 4-hydroxy-3-methoxyacetophenone, the 4-hydroxyl group was glucosylated and two dimerized glucosides, biphenyl and biphenylether types, were obtained in low yields. In acetophenone, 1-β-D-glucopyranosyloxy-1-phenylethane and 2-β-D-glucopyranosyloxyacetophenone were obtained. As mentioned above P. nil hairy roots showed various biotransformative activities including glucosylation of phenolic and benzylic hydroxyl groups, reduction of the formyl group near the benzene ring, and phenol oxidation dimerization. The glucosylation reaction was especially interesting for the production of valuable glucosides.

A study of substituent effects on the enantioselective trimethylsilylcyanation of benzaldehyde catalyzed by chiral Schiff base–titanium(IV) complexes

Abstract: New chiral Schiff base ligands derived from tert -butyl salicylaldehydes bearing electron withdrawing and donating groups were synthesized by reaction with various substituted chiral amino alcohols. These ligands were used with titanium tetraisopropoxide to study steric and electronic effects on the enantioselectivity of the trimethylsilylcyanation of benzaldehyde. ZINDO calculations are in agreement with the experimental results on the intermediate complexes, which indicate that the steric effects of the substituents are more important than the electronic ones.

Study of hydroxylation of benzene and toluene using a micro-DBD plasma reactor

Abstract: The hydroxylation behaviour of benzene and toluene were studied using a micro-plasma reactor, where an atmospheric non-thermal plasma was generated by a dielectric barrier discharge (DBD). The results indicated that oxidation products primarily consisted of phenol and C4-compounds for benzene hydroxylation, whereas cresol, benzaldehyde, benzylalcohol and C4-compounds were detected for toluene hydroxylation. By taking into consideration the reaction mechanism in the plasma reactor, these products were classified into (1) oxidation of the aromatic ring and functional group on the ring and (2) cleavage of the aromatic ring or dissociation of the functional group on the ring.

Synthesis of an enantiocomplementary catalyst of β-isocupreidine (β-ICD) from quinine

Abstract: Compound 20, a pseudoenantiomer of β-isocupreidine (β-ICD), was synthesized from quinine employing a Barton reaction of nitrosyl ester 13 and acid-catalyzed cyclization of carbinol 18 as key steps. The Baylis-Hillman reaction of benzaldehyde, p-nitrobenzaldehyde, and hydrocinnamaldehyde with 1,1,1,3,3,3-hexafluoroisopropyl acrylate (HFIPA) using 20 as a chiral amine catalyst was found to give the corresponding S-enriched adducts in high optical purity (>91% ee) in contrast to the β-ICD-catalyzed reaction which affords R-enriched adducts. This result suggests that compound 20 can serve as an enantiocomplementary catalyst of β-ICD in the asymmetric Baylis-Hillman reaction of aldehydes with HFIPA.

The direct, enantioselective, one-pot, three-component, cross-Mannich reaction of aldehydes: The reason for the higher reactivity of aldimine versus aldehyde in proline-mediated Mannich and aldol reactions

Abstract: In the proline-mediated Mannich and aldol reactions of propanal as a nucleophile, the aldimine prepared from benzaldehyde and p-anisidine is about 7 times more reactive than the corresponding alde- hyde, benzaldehyde, as an electrophile. This higher reactivity of aldimine over aldehyde is attributed to the carboxylic acid of proline protonating the basic ni- trogen atom of the aldimine more effectively than the oxygen atom of the aldehyde, an explanation which has been both experimentally and theoretically veri- fied.

Kinetic isotope effect evidence for the concerted transfer of hydride and proton from hydroxycyclopentadienyl ruthenium hydride in solvents of different polarities and hydrogen bonding ability

Abstract: The tolyl analogue of Shvo's hydroxycyclopentadienyl ruthenium hydride (4) efficiently transfers a hydride and proton to benzaldehyde or acetophenone to produce an alcohol. This reduction can be performed in toluene, methylene chloride, and THF. Reduction of benzaldehyde in toluene and methylene chloride occurs approximately 300 times faster than in THF at 0 °C. Reduction of acetophenone occurs between 75 and 150 times slower than benzaldehyde at 0 °C in each respective solvent. Despite the differences in rate, mechanistic studies have provided evidence for a similar concerted transfer of acidic and hydridic hydrogens in each solvent. Addition of water to THF led to further rate decrease coupled with an increase in the OH/D kinetic isotope effect and a decrease in the RuH/D kinetic isotope effect. Addition of excess alcohol to toluene or methylene chloride results in the significant retardation of the rate of reduction. The slower rate in THF and in the presence of alcohol is attributed to the stabilizati...