Showing papers on "Benzaldehyde published in 1995"

Catalysis of transition metal-functionalized hydrotalcites for the Baeyer-Villiger oxidation of ketones in the presence of molecular oxygen and benzaldehyde

Abstract: Multi-metallic hydrotalcites consisting of magnesium, aluminum, and iron, or copper elements were prepared, which catalyzed the Baeyer-Villiger oxidation using a combination system of molecular oxygen and benzaldehyde. In particular, the MgAlFeCO 3 hydrotalcite efficiently oxidized various cyclic ketones to give high yields of the corresponding lactones, while in the case of the MgAlCuCO 3 hydrotalcite, bicyclic ketones were oxidized almost quantitatively.

Asymmetric synthesis XXII: Asymmetric catalytic trimethylsilylcyanation of benzaldehyde by novel Ti(IV)-chiral schiff base complexes

Abstract: Benzaldehyde has been trimethylsilylcyanated with a catalyst prepared in situ from titanium tetraisopropoxide and a novel chiral Schiff base. Both (R) and (S) cyanohydrins are obtained in moderate e.e. values.

Thiol and disulfide derivatives of ephedra alkaloids 2: A mechanistic study of their effect on the addition of diethyl zinc to benzaldehyde

Abstract: Thiol and disulfide derivatives of ephedrine have been shown previously to catalyse in high enantiomeric excess (ee) the reaction of diethyl zinc with benzaldehyde. We find that this reaction involves non-linear correlations between the ee of product and catalyst. Osmotic measurements indicate a high degree of aggregation of the zinc thiolates. The behaviour of the thiol derivatives deviates sharply from that of the oxygen analogue, N-methyl ephedrine.

Enantioselective reformatsky reaction of methyl bromodifluoroacetate

Abstract: The Reformatsky reagent 2 generated from methyl bromodifluoroacetate is added to benzaldehyde in the presence of carbinols 3a, b, amino alcohols 3c-g, or amino alkoxide 3h. N-Methylephedrine 3c provides the highest enantioselectivity in the formation of the adduct S-4a (84% ee; >96% after recrystallization) whose absolute configuration is determined by an X-ray structural analysis of the amide 6.

Anaerobic oxidation of toluene (analogues) to benzoate (analogues) by whole cells and by cell extracts of a denitrifying Thauera sp.

Abstract: Toluene and related aromatic compounds can be mineralized to CO2 under anoxic conditions. Oxidation requires new dehydrogenase-type enzymes and water as oxygen source, as opposed to the aerobic enzymatic attack by oxygenases, which depends on molecular oxygen. We studied the anaerobic process in the denitrifying bacterium Thauera sp. strain K172. Toluene and a number of its fluoro-, chloro- and methyl-analogues were transformed to benzoate and the respective analogues by whole cells and by cell extracts. The transformation of xylene isomers to methylbenzoate isomers suggests that xylene degradation is similarly initiated by oxidation of one of the methyl groups. Toluene oxidation was strongly, but reversibly inhibited by benzyl alcohol. The in vitro oxidation of the methyl group was coupled to the reduction of nitrate, required glycerol for activity, and was inhibited by oxygen. Cells also contained benzyl alcohol dehydrogenase (NAD+), benzaldehyde dehydrogenase (NADP+), benzoate-CoA ligase (AMP-forming), and benzoyl-CoA reductase (dearomatizing). The toluene-oxidizing activity was induced when cells were grown anaerobically with toluene and also with benzyl alcohol or benzaldehyde, suggesting that benzyl alcohol or benzaldehyde acts as inducer. The other enzymes were similarly active in cells grown with toluene, benzyl alcohol, benzaldehyde, or benzoate. This is the first in vitro study of anaerobic oxidation of an aromatic hydrocarbon and of the whole-cell regulation of the toluene-oxidizing enzyme.

Enantioselective ortho-Lithiation of Aminals of benzaldehyde chromiumtricarbonyl complex

Abstract: The asymmetric ortho lithiation of aminals of benzaldehyde chromiumtricarbonyl complex is described. The best regioisomeric composition is attained with aminal 2d. Quenching with an electrophile and hydrolysis of the aminal back to the aldehyde afford a single enantiomer of the o-substituted benzaldehyde chromiumtricarbonyl complex.

Enantioselective Addition of Chirally Modified Allylboranes to N-(Trimethylsilyl)benzaldehyde Imine.

Abstract: Enantioselective allylation of N-(trimethylsilyl)benzaldehyde imine has been investigated by the use of optically active allylboron reagents including dialkyl 2-allyl-1,3,2-dioxaborolane-4,5-dicarboxylates (1) and B-allyldiisopinocampheylborane (2) to give the corresponding chiral homoallylamine with good yield in enantioselectivities up to 73% ee.

Acid zeolites as catalysts in organic reactions. Highly selective condensation of 2-alkylfurans with carbonylic compounds

Abstract: Condensation of 2-(3-acetoxypropyl)furan and 2-methylfuran with a series of aliphatic and aromatic carbonyl compounds, including formaldehyde, acetaldehyde, hexanal, cinnamaldehyde, benzaldehyde, anisaldehyde and acetone has been carried out in the presence of acid zeolites of medium and large pore size at different reaction temperatures. While H-ZSM-5 and H-MOR exhibited lower activity, we have found that tridirectional large pore zeolites Y and β are very convenient catalysts. In some cases, total conversion with complete selectivity could be achieved under our experimental conditions. Sulfuric acid was less active and selective for this type of Friedel-Crafts condensations. The resulting gem difurylalkanes with 3-hydroxypropyl substituent at the 2 position of the furan ring can be precursors of bis-spiroketals with potential activity as juvenile hormone antagonist for the Mediterranean fly.

Asymmetric addition of butyllithium to n-metallo imines of benzaldehyde

Abstract: N-Metallo imines derived from benzaldehyde such as N-aluminium imine, N-boryl imine and N-silyl imine were asymmetrically alkylated with butyllithium in the presence of chiral ligands including (−)-sparteine and proline-derived amino alcohols to give optically active 1-phenylpentyl-1-amine in up to 74 % enantiomeric excess. Polymer-supported chiral ligands were also used for the asymmetric addition.

FTIR studies of the interaction of aromatic hydrocarbons with vanadium oxide layered on ZrO2 and TiO2

Abstract: The reactivities of toluene, m-xylene, phenol and benzene on mono- and multi-layer V/Ti and V/Zr oxides prepared by the gas-phase method have been studied by FTIR spectroscopy. It is found that Lewis-acidic sites (vanadium ion) play an important role in the formation of π-complexes of toluene, m-xylene and benzene. The methyl group of the π-complex is dehydrogenated by the VO species to form benzyl species and benzaldehyde. On the other hand, phenol is adsorbed via its oxygen with its benzene ring oriented perpendicular to the surface. From spectral similarities, it is concluded that benzene is adsorbed to form mono- and/or disubstituted species. The activity of VO species on the monolayer catalyst is higher than that on the multilayer catalyst.

Affinity membrane introduction mass spectrometry

Abstract: A new technique, affinity membrane introduction mass spectrometry, is described. In this method, a chemically modified membrane is used to selectively adsorb analytes bearing a particular functional group and concentrate them from solution. Release of the bound analyte results in its transfer across the membrane and allows it to be monitored mass spectrometrically, using, in the present case, a benchtop ion trap instrument. Alkylamine-modified cellulose membranes are used to bind substituted benzaldehydes through imine formation at high pH. Release of the bound aldehyde is achieved by acid hydrolysis of the surface-bound imine. Benzaldehyde is detected with excellent specificity at 10 ppm in a complex mixture using this method. Using the enrichment capability of the membrane, a full mass spectrum of benzaldehyde can be measured at a concentration of 10 ppb. The behavior of a variety of other aldehydes is also discussed to illustrate the capabilities of the method. 21 refs., 5 figs., 2 tabs.

Pterin cofactor, substrate specificity, and observations on the kinetics of the reversible tungsten-containing aldehyde oxidoreductase fromClostridium thermoaceticum

Abstract: The αβ subunits of the tungsten-containing reversible aldehyde oxidoreductase ofClostridium thermoaceticum were shown to contain a pterin cofactor in the form of a mononucleotide. The substrate specificity of the enzyme for aliphatic and aromatic aldehydes and for carboxylates was broad. TheK m values for ethanal, propanal and butanal were 0.010–0.006 mM, but the value for methanal was 1.6 mM. Benzaldehyde derivatives with a hydroxy group in the 4-position showed millimolarK m values that were2–3 orders of magnitude higher than those of other aromatic and aliphatic aldehydes. The ratio ofk cat/Km for aldehydes and the corresponding acids is 104–105. For carboxylate reduction, 4-hydroxy benzoate again showed the highestK m value of all substrates tested. When the 4-hydroxy groups of the aldehyde and the acid were methylated, theK m values were decreased drastically. From the temperature dependence of carboxylate reduction at the expense of viologens, activation energies that depended on the substrate and on the applied viologen were calculated. The pH optima of the carboxylate reductions depended on the pK values of the acids and shifted to lower pH values with lower pK values of the acids. The ternary complex α3β3γ of the aldehyde oxidoreductase was able to dehydrogenate aldehydes to acylates with NADP+. Surprisingly the reverse reaction was observed too, although at very low rates. When exposed to air, the aldehyde oxidoreductase showed markedly enhanced lability in its reduced state compared to its oxidized state. With resting cells ofC. thermoaceticum, many carboxylates were reduced at the expense of carbon monoxide to the corresponding alcohols.

Synthesis of novel chiral diazole ligands for enantioselective addition of diethylzinc to benzaldehyde

Abstract: A variety of chiral pyrazole and imidazole derivatived ligands have been prepared under high pressure conditions and their catalytic efficiency in the enantioselective addition of diethylzinc to benzaldehyde has been examined.

A new model of capsule membrane phase transfer catalysis for oxidation of benzyl chloride to benzaldehyde with hydrogen peroxide

Abstract: This work deals with the theoretical and experimental aspects of the capsule membrane supported phase transfer catalysed (CM-PTC) oxidation of benzyl chloride to benzaldehyde using hydrogen peroxide (H 2 O 2 ) as the oxidizing agent. A new model is proposed for the CM-PTC oxidation of benzyl chloride using H 2 O 2 wherein the nucleophile (H 2 O 2 ) is transferred from the aqueous phase to the organic phase as a solvate of the catalyst which is supported on the capsule surface. This Langmuir-Hinshelwood type of model with the anchored-quaternary-H 2 O 2 complex as the active site was found to govern the rate of reaction.

Enantioselective ortho-lithiation of benzaldehyde chromiumtricarbonyl complex

Abstract: The asymmetric ortho lithiation of benzaldehyde chromiumtricarbonyl complex is performed by in situ temporary protection of the aldehyde functionality with a chiral amide and BuLi as metallating agent. Reaction with an electrophile followed by acidic hydrolysis leads to the enantiomerically enriched ortho substituted benzaldehyde chromiumtricarbonyl complex.

An enantioselective synthesis of the williams glycine template

Abstract: The Williams glycine template for amino acid synthesis, benzyl (2R,3S)-6-oxo-2,3-diphenyl-4-morpholinecarboxylate (1), was prepared in enantiomerically pure form in six steps from benzaldehyde in 48% overall yield. The initial chirality of the molecule was derived from oxynitrilase catalysed addition of HCN to benzaldehyde. A simple procedure for preparation of the biocatalyst is described.

Electrocatalytic oxidation of benzyl alcohol in alkaline medium on RuO2-coated titanium electrode

Abstract: The heterogeneous electrocatalytic redox behaviour of RuO2 electrodes fabricated by thermal decomposition is investigated with and without benzyl alcohol using cyclic voltammetric and potentiodynamic techniques. The cyclic voltammetric results show that benzyl alcohol oxidation is mediated by perruthenate ion electrogenerated at the electrode surface. Evaluation of kinetic parameters in relation to Tafel lines allows the postulation of a plausible reaction scheme in which benzyl alcohol adsorbs on the RuO2 electrode surface and the rate determining step is chemical reaction between perruthenate and adsorbed species. The reaction orders with respect to benzyl alcohol and OH− concentrations are 0.85 and 1, respectively. The results in galvanostatic electrolysis show that the major product for benzyl alcohol oxidation in an aqueous solution is benzaldehyde, and the organic yield is affected by such electrolysis conditions as t-butanol concentration, electrolysis current density, KOH concentration and electrolysis temperature.

Asymmetric synthesis XXV: Enantioselective synthesis of ethyl β -hydroxy -β -phenyl propanoate via an asymmetric reformatsky reaction

Abstract: Both stoichiometric and catalytic amounts of N,N-dialkyl derivatives of D or L-1,2-diphenyl aminoalcohols were used as chiral ligands in the enantioselective Reformatsky reaction of benzaldehyde with ethyl bromoacetate at reflux in the presence of ZnCu couple with e.e. up to 64%. The effects of ligand structure and solvents used on the enantioselectivity of the reaction were also studied.

Synthesis of new chiral catalysts, substituted 2-phenyl-5,6,7,8-tetrahydro-6,6-dimethyl-5,7-methano-quinolines, for the enantioselective addition of diethylzinc to benzaldehyde

Abstract: New chiral ligands, substituted 2-phenyl-5,6,7,8-tetrahydro-6,6-dimethyl-5,7-methano-quinolines, were prepared and the catalyzed reaction of diethylzinc with benzaldehyde was studied under various conditions to give 1-phenyl-1-propanol with up to 91% ee.