Topic
Benzaldehyde
About: Benzaldehyde is a research topic. Over the lifetime, 8049 publications have been published within this topic receiving 114520 citations. The topic is also known as: Benzoic acid aldehyde & Ethereal oil of bitter almonds.
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TL;DR: A new strategy in the design of new organic catalysts for direct asymmetric aldol reactions and related transformations is suggested as the calculations reveal that the amide N-H and the terminal hydroxyl groups form hydrogen bonds with the benzaldehyde substrate that cause high enantioselectivity.
Abstract: l-Prolinamides 2, prepared from l-proline and simple aliphatic and aromatic amines, have been found to be active catalysts for the direct aldol reaction of 4-nitrobenzaldehyde with neat acetone at room temperature. They give moderate enantioselectivities of up to 46% enantiomeric excess (ee). The enantioselectivity increases as the amide N—H becomes a better hydrogen bond donor. l-Prolinamides 3, derived from the reaction of l-proline with α,β-hydroxyamines such that there is a terminal hydroxyl group, show more efficient catalysis and higher enantioselectivities. In particular, catalyst 3h, prepared from l-proline and (1S,2S)-diphenyl-2-aminoethanol, exhibits high enantioselectivities of up to 93% ee for aromatic aldehydes and up to >99% ee for aliphatic aldehydes under –25°C. Model reactions of benzaldehyde with three enamines derived from the condensation of prolinamides with acetone have been studied by quantum mechanics calculations. The calculations reveal that the amide N—H and the terminal hydroxyl groups form hydrogen bonds with the benzaldehyde substrate. These hydrogen bonds reduce the activation energy and cause high enantioselectivity. Our results suggest a new strategy in the design of new organic catalysts for direct asymmetric aldol reactions and related transformations.
251 citations
TL;DR: One-pot synthesis of 5,10,15-triphenylcorrole has been achieved by reaction of benzaldehyde with an excess of pyrrole; the triphenylphosphinocobalt complex has been structurally characterized using X-ray crystallography as discussed by the authors.
251 citations
TL;DR: In this article, an 8% SiO2-TiO2 binary catalyst was used for the photocatalytic oxidation of gas-phase toluene and the presence of benzaldehyde and benzoic acid was identified on the surface of the deactivated photocatalyst.
246 citations
TL;DR: It is concluded that the mechanism of the reaction varies with catalysis or substituent effects, and the exceptional isotope effect observed experimentally was shown to be due to the rate-determining carbonyl addition caused by autocatalysis.
Abstract: The Baeyer-Villiger reaction of p-anisaldehyde with peroxyacetic acid in nonpolar solvents to give p-anisylformate was examined on the basis of ab initio molecular orbital calculations. To explain the experimental observations, the free-energy change was evaluated for each case in the absence and in the presence of an acid catalyst. It was found that, without catalysts, the rate-determining step corresponds to the carbonyl addition of peroxyacetic acid to p-anisaldehyde and the reaction hardly occurs. Acetic acid was found to catalyze the carbonyl addition and change the rate-determining step from the carbonyl addition to the migration of the carbonyl-adduct intermediate. Trifluoroacetic acid was observed to catalyze both the carbonyl addition and migration, and the carbonyl addition was demonstrated to be a rate-determining step. The results provided a convincing explanation of the complex kinetics seen experimentally. Further calculations were performed for the reaction of benzaldehyde with peroxyacetic acid to give phenylformate. Migratory aptitude was found to depend on the catalyst. Isotope effects were also investigated, and the exceptional isotope effect observed experimentally was shown to be due to the rate-determining carbonyl addition caused by autocatalysis. It is concluded that the mechanism of the reaction varies with catalysis or substituent effects.
244 citations
TL;DR: In this paper, a coupled system of selective oxidation of aromatic alcohols to aromatic aldehydes and reduction of nitrobenzene into aniline was realized using CdS/g-C 3 N 4 composite as a photocatalyst under visible light illumination.
Abstract: A coupled system of selective oxidation of aromatic alcohols to aromatic aldehydes and reduction of nitrobenzene into aniline was realized using CdS/g-C 3 N 4 composite as a photocatalyst under visible light illumination. The CdS/g-C 3 N 4 composite photocatalyst was prepared by hydrothermal method. The photocatalyst was characterized by x-ray powder diffraction (XRD), UV–vis diffuse reflection spectroscopy (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) specific surface area. Compared with single g-C 3 N 4 and CdS, the CdS/g-C 3 N 4 photocatalyst exhibits enhanced photocatalytic activity and excellent photostability under visible light illumination. It demonstrates that the selective oxidation of aromatic alcohol into aromatic aldehyde is achieved by direct holes oxidation, and the reduction of nitrobenzene into aniline is reached by direct electrons reduction. The optimum percentage of CdS is 10 wt.%. Under illumination for 4 h, the conversion of benzyl alcohol and the yield of benzaldehyde are about 48.0% and 44.6%, and the conversion of nitrobenzene and the yield of aniline are about 49.2% and 26.0%, respectively. The synergic effect of g-C 3 N 4 and CdS, which can effectively separate and transfer photoexcited carriers, was proposed to be responsible for the enhancement of the photocatalytic activity. This study has a guiding significance for the design of a coupled system which realizes selective oxidation and reduction of organics.
237 citations