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Corresponding Aldehydes (corresponding + aldehyde)
Selected AbstractsReinvestigation of the Mechanism of gem -Diacylation: Chemoselective Conversion of Aldehydes to Various gem -Diacylates and Their Cleavage under Acidic and Basic ConditionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2005Veerababurao Kavala Abstract The mechanism of gem -diacylate formation has been studied extensively using tetrabutylammonium tribromide (TBATB) as the catalyst. The reaction proceeds by a nucleophilic attack of an anhydride on an aldehydic carbonyl group, nucleophilic attack of the hemiacylate intermediate on a second molecule of the anhydride, followed by an intermolecular attack of a second acetate group to regenerate the anhydride. gem -Diacylates of various aliphatic and aromatic aldehydes were obtained directly from the reaction of a variety of aliphatic and aromatic acid anhydrides in the presence of a catalytic quantity of tetrabutylammonium tribromide (TBATB) under solvent-free conditions. A significant electronic effect was observed during its formation as well as deprotection to the corresponding aldehyde. Chemoselective gem -diacylation of the aromatic aldehyde containing an electron-donating group has been achieved in the presence of an aldehyde containing an electron-withdrawing group. Deprotection of the gem -diacylate to the parent carbonyl compound can be accomplished in methanol in presence of the same catalyst. Here again, chemoselective deprotection of the gem -diacylate of a substrate containing an electrondonating group has been achieved in the presence of a substrate containing an electron-withdrawing group. Both the acid and base stability order of the various gem -diacylates examined follow a similar order. The stability order determined from the present study is: gem -dibenzoate > gemdipivalate > gem -diisobutyrate > gem -diacetate > gem -dipropionate. All the gem -diacylals are more stable under basic conditions than acidic condition. No correlation was found between the stability order and the pKa's of the corresponding acids; rather, the stability order is directly related to the steric crowding around the carbonyl carbon. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] 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 ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-13 2005Yujiro Hayashi 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 aldehyde, benzaldehyde, as an electrophile. This higher reactivity of aldimine over aldehyde is attributed to the carboxylic acid of proline protonating the basic nitrogen atom of the aldimine more effectively than the oxygen atom of the aldehyde, an explanation which has been both experimentally and theoretically verified. [source] (4,4-Difluoro-4-bora-3a,4a,-diaza-s-indacen-3-yl)acetaldehyde: Synthesis and chemical propertiesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2009Mykola P. Shandura A reaction of 3,5-dimethylborondipyrromethene 3 with the DMF dimethylacetal gives rise to monoenamine 4. The latter is converted to the corresponding aldehyde 5. A considerable contribution of the enolic form of the aldehyde allows preparing numerous 3-vinyl substituted borondipyrromethenes and some heterocyclic derivatives. A reaction of the aldehyde 5 with tertiary aliphatic amines and the consecutive Hofmann-type decomposition of the intermediary quaternary salt give rise to the corresponding dialkylaminovinyl derivatives. J. Heterocyclic Chem., (2009). [source] Iron Chloride/4-Acetamido-TEMPO/Sodium Nitrite-Catalyzed Aerobic Oxidation of Primary Alcohols to the AldehydesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1 2010Weili Yin Abstract A variety of 4-substituted 2,2,6,6-tetramethylpiperidyl-1-oxy (TEMPO) derivatives has been screened for their ability in the oxidation of primary alcohols to the aldehydes with dioxygen under mild conditions. An evaluation of the efficiency of these 4-substituted TEMPO derivatives in the alcohol oxidation may allow an insight into the effect of the structural variations of TEMPO on the oxidation of alcohols, which should facilitate catalyst design and screening efforts. Based on the screening results of 4-substituted TEMPO derivatives, the catalyst comprised of 4-acetamido-TEMPO, iron chloride and sodium nitrite, has been developed for the highly efficient oxidation of a wide range of primary alcohols including primary aliphatic alcohols to the corresponding aldehydes under mild conditions. [source] Reusable Copper-Aluminum Hydrotalcite/rac -BINOL System for Room Temperature Selective Aerobic Oxidation of AlcoholsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009M. Lakshmi Kantam Abstract An efficient catalyst system consisting of copper-aluminum hydrotalcite/rac- BINOL ligand has been developed for the oxidation of alcohols using air as a green oxidant at room temperature. Various alcohols could be transformed into their corresponding aldehydes or ketones in good to excellent yields using the set of optimal conditions. This composite catalytic system can also be recovered and reused for several cycles without a significant loss of catalytic activity. [source] Trace Water-Promoted Oxidation of Benzylic Alcohols with Molecular Oxygen Catalyzed by Vanadyl Sulfate and Sodium Nitrite under Mild ConditionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2009Zhongtian Du Abstract An inexpensive catalytic system consisting of vanadyl sulfate and sodium nitrite was developed for the oxidation of benzylic alcohols with molecular oxygen under mild conditions. Benzyl alcohols with various substitutions were efficiently converted to their corresponding aldehydes with high conversion and selectivity under 80,°C (e.g., 4-nitrobenzyl alcohol was smoothly oxidized to 4-nitrobenzyl aldehyde with 94% yield under 0.5,MPa of molecular oxygen). Halogen, noble metals, extra base or complicated ligands were avoided. Addition of a trace of water to this system before the reaction was crucial for the high efficiency. [source] Synthesis of Aliphatic (S)-,-Hydroxycarboxylic Amides using a One-Pot Bienzymatic Cascade of Immobilised Oxynitrilase and Nitrile HydrataseADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2009Sander van Pelt Abstract A one-pot bienzymatic cascade combining a hydroxynitrile lyase (Manihot esculenta, E.C. 4.1.2.10) and a nitrile hydratase (Nitriliruptor alkaliphilus, E.C. 4.2.1.84) for the synthesis of enantiopure aliphatic ,-hydroxycarboxylic amides from aldehydes is described. Both enzymes were immobilised as cross-linked enzyme aggregates (CLEAs). Stability tests show that the nitrile hydratase CLEAs are sensitive to water-immiscible organic solvents as well as to aldehydes and hydrogen cyanide (HCN), but are remarkably stable and show useful activity in acidic aqueous environments of pH,4,5. The cascade reactions are consequently carried out by using a portionwise feed of HCN and moderate concentrations of aldehyde in acidic aqueous buffer to suppress the uncatalysed hydrocyanation background reaction. After optimisation, this method was used to synthesise five different kinds of aliphatic ,-hydroxycarboxylic amides from the corresponding aldehydes with good yields and with enantiomeric purities comparable to those obtained for the ,-hydroxynitriles in the microaqueous hydrocyanation using hydroxynitrile lyase and an excess of HCN. [source] Photooxidation of Benzyl Alcohols with Immobilized FlavinsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Harald Schmaderer Abstract Benzyl alcohols are oxidized cleanly and efficiently to the corresponding aldehydes under irradiation using flavin photocatalysts and aerial oxygen as the terminal oxidant in homogeneous aqueous solution. Turnover frequencies (TOF) of more than 800,h,1 and turnover numbers (TON) of up to 68 were obtained. Several flavin photocatalysts with fluorinated or hydrophobic aliphatic chains were immobilized on solid supports like fluorous silica gel, reversed phase silica gel or entrapped in polyethylene pellets. The catalytic efficiency of the heterogeneous photocatalysts was studied for the oxidation of different benzyl alcohols in water and compared to the analogous homogeneous reactions. Removal of the heterogeneous photocatalyst stops the reaction conversion immediately, which shows that the immobilized flavin is the catalytically active species. The immobilized catalysts are stable, retain their reactivity if compared to the corresponding homogeneous systems and are easily removed from the reaction mixture and reused. TOF of up to 26,h,1, TON of 280 and up to 3 reaction cycles without loss of activity are possible with the heterogeneous flavin photocatalysts. [source] Creation of a Monomeric Ruthenium Species on the Surface of Micro-Size Copper Hydrogen Phosphate: An Active Heterogeneous Catalyst for Selective Aerobic Oxidation of AlcoholsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2007Junhua Liu Abstract A new micro-size copper hydrogen phosphate (CHP) synthesized by the emulsion method combined with a monomeric ruthenium species was found to be a very effective catalyst for the selective oxidation of alcohols. Several kinds of alcohols were transformed into the corresponding aldehydes or ketones over the RuCHP catalyst by oxygen under very mild conditions. The results showed that the CHP material was perfect as a catalyst support due to its high ion-exchange ability and adsorption capacity. [source] Synthesis, characterization and catalytic studies of ruthenium(II) chalconate complexesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 2 2009M. Muthukumar Abstract Stable ruthenium(II) carbonyl complexes of the type [RuCl(CO)(EPh3)(B)(L)] (E = P or As; B = PPh3, AsPh3 or Py; L = 2,-hydroxychalcones) were synthesized from the reaction of [RuHCl(CO)(EPh3)2(B)] (E = P or As; B = PPh3, AsPh3 or Py) with 2,-hydroxychalcones in benzene under reflux. The new complexes were characterized by analytical and spectroscopic (IR, electronic 1H, 31P and 13C NMR) data. They were assigned an octahedral structure. The complexes exhibited catalytic activity for the oxidation of primary and secondary alcohols into their corresponding aldehydes and ketones in the presence of N -methylmorpholine- N -oxide (NMO) as co-oxidant and were also found to be efficient transfer hydrogenation catalysts. Copyright © 2008 John Wiley & Sons, Ltd. [source] Novel structural features in the GMC family of oxidoreductases revealed by the crystal structure of fungal aryl-alcohol oxidaseACTA CRYSTALLOGRAPHICA SECTION D, Issue 11 2009Israel S. Fernández Lignin biodegradation, a key step in carbon recycling in land ecosystems, is carried out by white-rot fungi through an H2O2 -dependent process defined as enzymatic combustion. Pleurotus eryngii is a selective lignin-degrading fungus that produces H2O2 during redox cycling of p -anisylic compounds involving the secreted flavoenzyme aryl-alcohol oxidase (AAO). Here, the 2.4,Ĺ resolution X-ray crystal structure of this oxidoreductase, which catalyzes dehydrogenation reactions on various primary polyunsaturated alcohols, yielding the corresponding aldehydes, is reported. The AAO crystal structure was solved by single-wavelength anomalous diffraction of a selenomethionine derivative obtained by Escherichia coli expression and in vitro folding. This monomeric enzyme is composed of two domains, the overall folding of which places it into the GMC (glucose,methanol,choline oxidase) oxidoreductase family, and a noncovalently bound FAD cofactor. However, two additional structural elements exist in the surroundings of its active site that modulate the access of substrates; these are absent in the structure of the model GMC oxidoreductase glucose oxidase. The folding of these novel elements gives rise to a funnel-like hydrophobic channel that connects the solvent region to the buried active-site cavity of AAO. This putative active-site cavity is located in front of the re side of the FAD isoalloxazine ring and near two histidines (His502 and His546) that could contribute to alcohol activation as catalytic bases. Moreover, three aromatic side chains from two phenylalanines (Phe397 and Phe502) and one tyrosine (Tyr92) at the inner region of the channel form an aromatic gate that may regulate the access of the enzyme substrates to the active site as well as contribute to the recognition of the alcohols that can effectively be oxidized by AAO. [source] Expression, purification and crystallization of a thermostable short-chain alcohol dehydrogenase from the archaeon Thermococcus sibiricusACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 6 2010A. V. Lyashenko Alcohol dehydrogenases belong to the oxidoreductase family and play an important role in a broad range of physiological processes. They catalyze the cofactor-dependent reversible oxidation of alcohols to the corresponding aldehydes or ketones. The NADP-dependent short-chain alcohol dehydrogenase TsAdh319 from the thermophilic archaeon Thermococcus sibiricus was overexpressed, purified and crystallized. Crystals were obtained using the hanging-drop vapour-diffusion method using 25%(w/v) polyethylene glycol 3350 pH 7.5 as precipitant. The crystals diffracted to 1.68,Ĺ resolution and belonged to space group I222, with unit-cell parameters a = 55.63, b = 83.25, c = 120.75,Ĺ. [source] A new crystal form of human diamine oxidaseACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 2 2010Aaron P. McGrath Copper amine oxidases (CAOs) are ubiquitous in nature and catalyse the oxidative deamination of primary amines to the corresponding aldehydes. Humans have three viable CAO genes (AOC1,3). AOC1 encodes human diamine oxidase (hDAO), which is the frontline enzyme for histamine metabolism. hDAO is unique among CAOs in that it has a distinct substrate preference for diamines. The structure of hDAO in space group P212121 with two molecules in the asymmetric unit has recently been reported. Here, the structure of hDAO refined to 2.1,Ĺ resolution in space group C2221 with one molecule in the asymmetric unit is reported. [source] A novel oxygen-dependent deoximation by nitric oxideCHINESE JOURNAL OF CHEMISTRY, Issue 5 2000Yu-Zhu Mao Abstract A variety of aldoximes and ketoximes were oxidized to corresponding aldehydes and ketones by nitric oxide in the presence of oxygen. A presumed mechanism was suggested. [source] | ||||||||||||||||||||||