Showing papers on "Benzaldehyde published in 1997"
TL;DR: All experimental evidence points to a mechanism involving an N-acyliminium ion as the key intermediate, formed by acid-catalyzed condensation of benzaldehyde and urea (or N-methylurea) formed by the Biginelli dihydropyrimidines.
Abstract: The mechansim of the three-component Biginelli dihydropyrimidine synthesis was reinvestigated using 1H and 13C NMR spectroscopy. Condensation of benzaldehyde, ethyl acetoacetate, and urea (or N-methylurea) in CD3OH according to the procedure described by Biginelli produced the expected 6-methyl-2-oxo-4-phenyl-1,2,3,4-tetrahydropyrimidine-5-carboxylates. According to NMR measurements, there is no evidence that the first step in the Biginelli reaction is an acid-catalyzed aldol reaction of ethyl acetoacetate and benzaldehyde leading to a carbenium ion intermediate, as has been suggested previously. In contrast, all experimental evidence points to a mechanism involving an N-acyliminium ion as the key intermediate, formed by acid-catalyzed condensation of benzaldehyde and urea (or N-methylurea). Interception of this iminium ion by ethyl acetoacetate produces open-chain ureides which subsequently cyclize to the Biginelli dihydropyrimidines.
383 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, the initial steps in the photocatalytic oxidation (PCO) of benzene, toluene, p-xylene, mesitylene, benzyl alcohol, benzaldehyde, and m-cresol adsorbed on a thin film of TiO2 catalyst were studied.
Abstract: Transient reaction at 273 and 300 K was used to study the initial steps in the photocatalytic oxidation (PCO) of benzene, toluene, p-xylene, mesitylene, benzyl alcohol, benzaldehyde, and m-cresol adsorbed on a thin film of TiO2 catalyst. Adsorbed aromatics were oxidized by O2 photocatalytically in the absence of gas-phase aromatics, and the compounds remaining on the surface were characterized by temperature-programmed oxidation and desorption (TPO, TPD). Benzene and methyl benzenes oxidize rapidly at 273 or 300 K to form adsorbed intermediates that are more strongly adsorbed and much less reactive than the original aromatic, which is relatively weakly adsorbed on TiO2. The catalyst is expected to be covered with these intermediates during steady-state reaction. The rates of PCO of benzene and methyl benzenes to CO2 are slow relative to complete oxidation of alcohols or chlorinated hydrocarbons. The intermediates do not appear to be alcohols or aldehydes formed by oxidation of a methyl group, nor do they correspond to addition of an hydroxyl to the aromatic ring. Benzyl alcohol oxidizes photocatalytically to benzaldehyde and then to CO2 and H2O during PCO, but adsorbed m-cresol does not photocatalytically oxidize.
98 citations
TL;DR: In this article, the results indicated that the lanthanides in aqueous solution exchanged with almost all the cations (H+ or Na+) on the resins to form stable ionic complexes.
Abstract: Lanthanide(III) catalysts supported on ion exchange resins (Ln-resins) were prepared from Dowex, Amberlite, Amberlyst, and other cation exchange resins. The amount of lanthanides on resin supports was measured through EDTA titration. The results indicated that the lanthanides in aqueous solution exchanged with almost all the cations (H+ or Na+) on the resins to form stable ionic complexes between the lanthanides(III) and the resins. The effects of resin types, resin sizes, and lanthanide salts were investigated with a reaction of indole and hexanal in aqueous solution and with an aldol reaction of benzaldehyde and silyl enol ether in organic solvents. The study found that among ion exchange resins tested Amberlyst XN-1010 and Amberlyst 15 complexed with lanthanides(III) were the most effective catalysts. In addition, the selective Ln-resins were utilized to catalyze acetalization of aldehydes, aldol reaction of formaldehyde or benzaldehyde in aqueous solution, nucleophilic addition to an imine, allylation...
89 citations
TL;DR: In this article, a simple Langmuir-Hinshelwood model invoking the addition of the second H atom to benzaldehyde as the rate-determining step fit the data well.
86 citations
TL;DR: The role of these two NAD+-ribose-binding residues was investigated, and a pre-steady state burst of NADH formation was observed for the E399Q/K and K192Q mutants with benzaldehyde, and p-nitrobenzaldehyde was oxidized faster than benzaldehyde so that when aromatic aldehydes were used as substrates, the rate-limiting step remained deacylation for all these mutants.
82 citations
TL;DR: In this article, the Cannizzaro reaction was used to determine the mobility of surface hydroxyl groups on simple metal oxides, such as ZnO and Cr 2 O 3, in a helium or dihydrogen atmosphere.
69 citations
TL;DR: In this article, optically active amino alcohols have been obtained from CeCl 3 -activated (+)-camphor and (−)-fenchone and N-functionalized organolithium compounds, which catalyzes the addition of diethylzinc to benzaldehyde in high yields and enantioselectivities up to 64%.
Abstract: New optically active aminoalcohols have been prepared from CeCl 3 -activated (+)-camphor and (−)-fenchone and N-functionalized organolithium compounds. The aminoalcohols obtained catalyze the addition of diethylzinc to benzaldehyde in high yields and enantioselectivities up to 64%.
67 citations
TL;DR: The resolved benzaldehyde was synthesized in seven steps from p-benzoquinone and cyclopentadiene and included a resolution via diastereomeric ketals as discussed by the authors.
63 citations
TL;DR: In this article, an asymmetrically trimethylsilylcyanated benzaldehyde was used to obtain a high level of efficiency using chiral (salen)Ti(IV) catalysts.
Abstract: Benzaldehyde has been asymmetrically trimethylsilylcyanated, using chiral (salen)Ti(IV) catalysts 1a and 1b, 2a and 2b, 3a and 3b prepared in situ from titanium tetraisopropoxide and the Schiff's bases derived from (R)- or (S)-4-hydroxy-5-formyl[2.2]paracyclophane [(R)- and (S)-FHPC] and diaminoethane (EDA) (catalysts 1a or 1b); (R)- or (S)-FHPC and 1,3-diaminopropane (PDA) (catalysts 2a or 2b); (R)- or (S)-FHPC and (1R,2R)-1,2-diaminocyclohexane [(1R,2R)-CHDA] (catalysts 3a and 3b). Surprisingly, 1a and 1b were found to be the most efficient catalysts whereas both enantiomers of 2 were completely inactive. The maximum e.e. of 84% (S) at −78°C was obtained in the reaction catalysed by 1b at 5–10 mol%. The catalyst could be precipitated with hexane from the reaction mixture and reused.
62 citations
TL;DR: The electron rich benzaldehyde derivatives 4-hydroxybenzaldehyde and 2-methoxy-4-hydroxienzaldehyde have been investigated for use as linkers for solid phase organic synthesis as mentioned in this paper.
TL;DR: Turnover frequencies, activation energies and reaction orders for crotonaldehyde, benzaldehyde, phenylacetaldehyde and acetophenone are provided and compared to those for butyraldehyde, benzyl alcohol, 1-phenylethanol, acetylcyclohexane and acetone.
Abstract: The vapor–phase hydrogenation of a group of aldehydes and ketones which contain unsaturated C=C bonds has been studied over a family of supported Pt catalysts. Turnover frequencies, activation energies and reaction orders for crotonaldehyde, benzaldehyde, phenylacetaldehyde and acetophenone are provided and compared to those for butyraldehyde, benzyl alcohol, 1–phenylethanol, acetylcyclohexane and acetone. Metal–support interactions (MSI) induced in Pt/TiO2 not only enhance specific activity but also markedly shift selectivity because hydrogenation of the carbonyl bond is favored. The retention of high selectivity to the intermediate unsaturated alcohols shows that adsorption properties, as well as kinetic parameters, are altered. A model is discussed which describes the sites responsible for this behavior.
TL;DR: In this paper, the formation of surface intermediates, appearing during the interaction of vanadyl pyrophosphate (VO) 2 P 2 O 7 with feed components of the toluene ammoxidation was studied by FTIR spectroscopy.
Abstract: The mechanism of formation of surface intermediates, appearing during the interaction of vanadyl pyrophosphate (VO) 2 P 2 O 7 with feed components of the toluene ammoxidation was studied by FTIR spectroscopy. The investigation of ammonia adsorption at elevated temperature showed protonated and coordinated ammonia as expected as well as the generation of amido species; all could be so called ‘nitrogen insertion species’ or a source of these at least. The interaction of toluene and possible reaction intermediates such as benzaldehyde and benzylamine with (VO) 2 P 2 O 7 was studied. The investigations revealed that the ammoxidation of toluene probably proceeds via the formation of a benzaldehyde intermediate. Afterwards, benzylimine surface species were probably formed by a N-insertion, using NH + 4 surface species followed by the formation of benzonitrile by subsequent oxidative dehydrogenation. However, no benzamide species were observed. The surface species generated upon adsorption of benzaldehyde were similar to those formed from toluene, indicating the role of the former as intermediate in the nitrile formation path. Otherwise, the adsorption of benzylamine in the presence of oxygen did not lead to the formation of benzonitrile. Therefore, an ammoxidation mechanism of toluene via a benzaldehyde intermediate is preferred and reaction pathways via benzamide or benzylamine as intermediates seem to be improbable.
TL;DR: In this paper, the detection of adulterated bitter almonds and cinnamon oils can be achieved by means of the SNIF-NMR method using benzaldehyde as a molecular probe.
Abstract: The detection of adulterated bitter almond and cinnamon oils can be achieved by means of the SNIF-NMR method using benzaldehyde as a molecular probe. It is demonstrated that the site specific deuterium contents of benzaldehyde allow the determination of the origin of the molecule: synthetic (ex-toluene and ex-benzal chloride), natural (ex-kernels from apricots, peaches, and cherries and ex-bitter almond) and semisynthetic (ex-cinnamaldehyde extracted from cinnamon). A strategy resorting to the transformation of cinnamaldehyde into benzaldehyde has been exploited to study the origin of cinnamaldehyde. An analytical method for routine characterization of the genuineness of bitter almond and cinnamon oils is proposed. The repeatability of the 2H-NMR measurements on benzaldehyde and the capability for both proving and quantifying adulterations are estimated. Keywords: Benzaldehyde; cinnamaldehyde; bitter almond oil; cinnamon oil; SNIF-NMR; authentication; adulteration; retroaldolization
TL;DR: In this article, an enantioselective alkylation of benzaldehyde with Et2Zn has been studied, which is catalyzed by helical titanium complexes of tetradentate ligands.
TL;DR: Chiral 2-(1-p -tolylsulfinyl)alkylpyridines and corresponding sulfide-pyridsines were prepared and assessed in the enantioselective palladium catalyzed allylic substitution of 1,3-diphenylprop-2-enyl acetate with dimethylmalonate and addition of diethylzinc to benzaldehyde as mentioned in this paper.
TL;DR: In this paper, the straightforward synthesis of new enantiopure γ-aminoalcohols through 1,3-dipolar cycloadditon to a chiral cyclic nitrone derived from l -malic acid is described.
Abstract: The straightforward synthesis of new enantiopure γ-aminoalcohols through 1,3-dipolar cycloadditon to a chiral cyclic nitrone derived from l -malic acid is described. Results of the application of these compounds as chiral catalysts in the alkylation of benzaldehyde with diethylzinc are also reported.
TL;DR: In this paper, a new pathway for the simple, stereocontrolled and economical synthesis of (±)-1 from benzaldehyde is described, and the structures of two intermediates have been revised to those shown in Scheme 2.
TL;DR: In this paper, the kinetics and mechanism of liquid−liquid phase transfer catalyzed oxidation of benzyl chloride with chromate salts are investigated in great detail in a systematic way to throw light on the selectivity of the reaction to benzaldehyde.
Abstract: The kinetics and mechanism of liquid−liquid phase transfer catalyzed oxidation of benzyl chloride with chromate salts is investigated in great detail in a systematic way to throw light on the selectivity of the reaction to benzaldehyde. This system presents a complex case of consecutive and parallel reactions in which benzyl alcohol is formed as an intermediate which is further oxidized to benzaldehyde. The results are novel, and the experimental data fit the theoretical model very well.
TL;DR: In this paper, the reaction of (R,R)-(+)-1,3-dithiane-1, 3-dioxide with aldehydes has been carried out and the dithiane dioxide moiety elaborated further.
TL;DR: In this article, the gas phase hydrogen treatment of benzaldehyde and o -tolualdehyde was studied over a Ni/SiO 2 catalyst prepared by homogeneous precipitation/deposition.
Abstract: The gas phase hydrogen treatment of benzaldehyde and o -tolualdehyde was studied over a Ni/SiO 2 catalyst prepared by homogeneous precipitation/deposition. The reactions were conducted in the absence of diffusion limitations and reproducible turnover frequencies are presented. The products generated resulted from the hydrogenation and hydrogenolysis of the substituent CO bond and from the hydrogenolysis of the aryl-carbonyl CC bond, the aromatic ring remaining intact. The temperature dependencies of the rate constant and product selectivity are illustrated and apparent activation energies for hydrogenation to the aromatic alcohol are given. The influence of the ortho -substituted methyl group on the reactivity of the carbonyl function is discussed. The reaction of benzyl alcohol and 2-methylbenzyl alcohol over the same catalyst was investigated and the overall reaction pathway is identified.
TL;DR: In this paper, a product study of the photooxidation of the aromatic sulfides 1−5 sensitized by TiO2 in MeCN, in the presence of Ag2SO4, has been carried out.
Abstract: A product study of the photooxidation of the aromatic sulfides 1−5 sensitized by TiO2 in MeCN, in the presence of Ag2SO4, has been carried out. With benzyl phenyl sulfide (1), 4-methoxybenzyl phenyl sulfide (2), and phenethyl phenyl sulfide (4), the photooxidation led mainly to aldehydic products, benzaldehyde, 4-methoxybenzaldehyde, and phenylacetaldehyde, respectively. With benzyl 4-methoxyphenyl sulfide (3), the major product was the corresponding sulfoxide. Diphenyl sulfoxide was the only product observed in the oxidation of diphenyl sulfide (5). These results suggest α-C−H deprotonation as the major reaction path for the radical cations of 1, 2, and 4, and an active role in this respect of the oxygenated basic sites present on the TiO2 surface is envisaged. An interaction of these oxygenated centers with the sulfur atom of the adsorbed radical cation is also suggested to explain the remarkable finding that substantial amounts of sulfoxide are observed with 3 and 5, in spite of the fact that the photo...
TL;DR: In this article, an intermediate oxaziridine 5 that rearranges via acid-catalysed ON bond cleavage was proposed. But it is not known whether the precursors of these intermediates are N-disubstituted or C-s-alkyl.
TL;DR: A range of chiral tellurium compounds having an azomethine functional group in the position ortho to telluria have been synthesized by the reaction of aldehydes bis(o-formylphenyl) telluride and o-(butyltelluro)benzaldehyde.
TL;DR: Bis(tosyl)imidoruthenium(VI) porphyrin complexes are prepared and characterised by spectroscopic means as discussed by the authors and can undergo imido group transfer reactions with======alkenes to afford aziridines, as well as C-H bond oxidation of======benzyl alcohol to give benzaldehyde.
TL;DR: In this paper, the aldehyde sorption and desorption kinetics of acetaldehyde, benzaldehyde, and salicylalde- hyde have been investigated under different conditions.
Abstract: Chlorosulfonated styrene (10%) divinylbenzene resin beads reacted with an excess of ethylenediamine (EDA), diethylenetriamine (DETA), and triethylenetet- ramine (TETA) to give the corresponding sulfonamides with pendant oligo(ethylenei- mines). The resulting modified resins are useful in the separation of aldehydes from hydrocarbon mixtures. Sorption of aldehydes occurs through formation of both Schiff base and five-membered (imidazoline) rings. Sorbed aldehydes can readily be stripped from the resins by treating with dilute acid solutions. Since the sulfamide bond has a reasonable stability toward acid-base hydrolysis, the loaded resins can be regenerated and recycled by simple acid-base washings, without losing their activity. In the present study, sorption and desorption kinetics of acetaldehyde, benzaldehyde, and salicylalde- hyde have been investigated under different conditions. The aldehyde sorption obeys second-order kinetics. The method presented is applicable for all aromatic aldehydes. However, in the case of aliphatic aldehydes carrying an a-hydrogen, aldol condensation products form in solution. So aliphatic aldehydes and their aldol products are sorbed together by the resins. This limits the recovery of aliphatic aldehydes. Consequently, the resins described are cost effective sorbents for the removal and recovery of aromatic aldehydes from various mixtures. q 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2857-2864, 1997
TL;DR: In this paper, the absorption spectra of the intermediate transients formed in the reactions of •OH and SO4•- with all three compounds are similar with a peak around 370−380 nm.
Abstract: Radiation chemical reactions of •OH, O•-, and SO4•- with benzaldehyde, acetophenone, and benzophenone have been studied using both pulse and steady-state radiolysis techniques. The observed rates for the •OH addition (k = (2.6−8.8) × 109 M-1 s-1) are higher than those found for the SO4•- reaction (k = (0.7−4.0) × 109 M-1 s-1). The rate for the reaction of O•- with benzaldehyde is higher than that found for •OH, while a reverse trend is observed in the case of the two ketones. Optical absorption spectra of the intermediate transients formed in the reactions of •OH and SO4•- with all three compounds are similar with a peak around 370−380 nm. The absorption spectra from the O•- reaction have shown a major peak at 310 nm and are somewhat different from those obtained in the reaction of •OH. The yields of the phenolic products formed in the reaction of •OH with benzaldehyde and acetophenone in the presence of 0.1 mM ferricyanide corresponded to only 30% and 50% •OH yields, respectively. Benzoic acid is a major...
TL;DR: Asymmetric catalytic ethylation of benzaldehyde utilizing a series of tetradental bis-β-amino alcohols based on the octahydro-cyclopenta[ b ]pyrrole system is presented in this paper.
Abstract: Asymmetric catalytic ethylation of benzaldehyde utilizing a series of new, tetradental bis-β-amino alcohols based on the octahydro-cyclopenta[ b ]pyrrole system—derived from an industrial waste material—is presented. Attention is focused on steric aspects of the catalyst(-precursor) structure. Furthermore, the catalytic efficiency of the ethylene-bridged, C 2 -symmetrical bis-β-amino alcohols is compared to related ‘monomeric’ structures. Potent chiral ligands, which are highly effective even at concentrations of below 2 mol%, have been developed reaching excellent enantioselectivities up to 100% ee.
TL;DR: In this article, the oxides of Mg, Pb, Cr, La, Pr, Yb, Mn, Fe, Co, Zn, Zr and Ce were studied as catalysts for the reactions of benzoic acid in the temperature range 523-723 K. All experiments were performed in a continuous flow apparatus, at a total pressure of about one bar, with hydrogen as the reductant.