- Selective reduction of carboxylic acids to aldehydes catalyzed by B(C 6F5)3
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B(C6F5)3 efficiently catalyzes hydrosilylation of aliphatic and aromatic carboxylic acids to produce disilyl acetals under mild conditions. Catalyst loadings can be as low as 0.05 mol %, and bulky tertiary silanes are favored to give selectively the acetals. Acidic workup of the disilyl acetals results in the formation of aldehydes in good to excellent yields.
- Bezier, David,Park, Sehoon,Brookhart, Maurice
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p. 496 - 499
(2013/03/29)
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- Efficient reduction of esters to aldehydes through iridium-catalyzed hydrosilylation
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Trumping DIBALH: A new method for reduction of esters to aldehydes through silyl acetal intermediates involves a single-step hydrosilylation catalyzed by a readily available iridium complex, [{Ir(coe)2Cl}2] (see scheme; coe=cyclooctene). The low catalyst loading, mild reaction conditions, high conversions, and broad substrate scope make this method a superior alternative to ester reduction using DIBALH.
- Cheng, Chen,Brookhart, Maurice
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supporting information
p. 9422 - 9424
(2012/10/30)
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- Kinetics and mechanism of the oxidation of aliphatic primary alcohols by imidazolium fluorochromate
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The oxidation of nine aliphatic primary alcohols by imidazolium fluorochromate (IFC) in dimethylsulphoxide leads to the formation of corresponding aldehydes. The reaction is first order with respect to IFC. A Michaelis-Menten type kinetics is observed with respect to alcohols. The reaction is promoted by hydrogen ions; the hydrogen-ion dependence has the form : kobs = a + b [H+]. The oxidation of [1,1- 2H2]ethanol (MeCD2OH) exhibits a substantial primary kinetic isotope effect (kH/kD = 5.87 at 298 K). The reaction has been studied in nineteen different organic solvents. The solvent effect was analysed using Taft's and Swain's multiparametric equations. The rate of oxidation is susceptible to both polar and steric effects of the substituents. A suitable mechanism has been proposed.
- Gehlot,Gilla,Mishra,Sharma, Vinita
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experimental part
p. 685 - 692
(2012/04/04)
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- Oxidation of aliphatic primary alcohols by morpholinium chlorochromate: A kinetic and mechanistic approach
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The oxidation of nine aliphatic primary alcohols by morpholinium chlorochromate (MCC) in dimethylsulfoxide leads to the transformation of alcohols to the corresponding aldehydes. The reaction is first order with respect to both MCC and the alcohol both. The reaction is catalysed by hydrogen ions. The hydrogen-ion dependence has the form: kobs = a + A[H +]. The oxidation of [1,1-2H2]ethanol (MeCD2OH) exhibits a substantial primary kinetic isotope effect. The reaction has been studied in nineteen different organic solvents. The solvent effect was analysed using Taft's and Swain's multiparametric equations. The rate of oxidation is susceptible to both polar and steric effects of the substituents. A suitable mechanism has been proposed.
- Choudhary,Yajurvedi,Soni,Agarwa,Sharma, Vinita
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experimental part
p. 1061 - 1066
(2011/05/05)
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- Oxidation of unactivated primary aliphatic amines catalyzed by an electrogenerated 3,4-azaquinone species: A small-molecule mimic of amine oxidases
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High catalytic performance of the electrogenerated amine oxidase mimic 3,4-iminoquinone 1ox is observed under metal-free conditions in the chemoselective oxidation reaction of unactivated primary aliphatic amines.
- Largeron, Martine,Neudorffer, Anne,Fleury, Maurice-Bernard
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p. 1026 - 1029
(2007/10/03)
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- A comprehensive investigation of variations in melting ranges and NMR data of 2,4-dinitrophenylhydrazine derivatives
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The well-known characterization method of aldehydes and ketones utilizing their 2,4-dinitrophenylhydrazones (DNPs) often gives variable melting ranges and conflicting results for a single derivative. We have found that the DNPs melting point discrepancies and the irreproducibility of the method are mainly due to syn-anti (E-Z) isomerization caused by traces of acids which remain in the products when prepared by the conventional methods. A bicarbonate washing of the DNPs removes the acid, stabilizes the melting range and reproducibly gives higher-melting derivatives. In the DNP preparations of aldehydes and some unsymmetrical ketones only the kinetically favored (and also thermodynamically more stable) syn (E) isomer is formed. The six different melting ranges of acetaldehyde DNP (AA-DNP) previously reported by other investigators are correlated with the amounts of acid present in their DNP crystals. Derivatives with higher concentrations of acid(s) give lower melting ranges. In the presence of small amounts of acid, E-Z isomerization occurs in most solvents but not in methanol or dimethyl sulfoxide (DMSO). Larger amounts of acid cause the isomerization in all solvents, but the process is much slower in the aforementioned solvents. Alcohols, but not chlorinated solvents, are suitable for the DNPs recrystallization. E-Z isomerization of AA-DNP also occurs thermally by first order kinetics when its pure E isomer is heated at its melted state. An equilibrium ratio of 2:1 (E:Z) is reached after 10 minutes. A substantial decrease (up to 2.05 ppm) is observed for the NMR chemical shifts of the AA-DNPs protons in benzene and electron rich aromatic solvents compared to those obtained in chloroform, acetonitrile, acetone, methanol, DMSO or even cyclohexane and electron deficient nitrobenzene. An explanation is given for the drastic chemical shift changes.
- Tayyari, Sayyed Faramarz,Speakman, Jeffrey L.,Arnold, Macklin B.,Cai, Wen,Behforouz, Mohammad
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p. 2195 - 2200
(2007/10/03)
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- Transformation of acid chlorides into aldehydes by reduction of in-situ formed acyltributylphosphonium ions with zinc-copper couple or zinc
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Transformation of acid chlorides into the corresponding aldehydes without over-reduction to alcohols was effectively achieved by the reduction of acyltributylphosphonium ions, formed in-situ from the chlorides and tributylphosphine in CH3CN, with Zn-Cu couple or Zn in the presence of CH3SO3H under an N2 atmosphere.
- Maeda, Hatsuo,Maki, Toshihide,Ohmori, Hidenobu
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p. 2247 - 2250
(2007/10/02)
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- The Chemistry of Pentavalent Organobismuth Reagents. Part 8. Phenylation and Oxidation of Alcohols by Tetraphenylbismuth Esters
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Tetraphenylbismuth trifluoroacetate under neutral or slightly acidic conditions O-phenylates primary alcohols in reasonable (65-75percent) yield, but gives only moderate yields with secondary alcohols and no O-phenylation with tertiary alcohols.An SN2 type mechanism is proposed with attack of oxygen on aryl carbon.In contrast, the reaction of Bi(V) reagents with alcohols under basic conditions gives, exclusively, oxidation, often with benzene as a leaving group.The presence of a Bi(V) intermediate with a bismuth-oxygen bond has been proved in several different ways using n.m.r. spectroscopy.Thus the reactions of alcohols with Bi(V) reagents parallel the corresponding reactions with phenols.
- Barton, Derek H. R.,Finet, Jean-Pierre,Motherwell, William B.,Pichon, Clotilde
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p. 251 - 260
(2007/10/02)
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