- Radical chain reduction of alkylboron compounds with catechols
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The conversion of alkylboranes to the corresponding alkanes is classically per-formed via protonolysis of alkylboranes. This simple reaction requires the use of severe reaction conditions, that is, treatment with a carboxylic acid at high temperature (>150 °C). We report here a mild radical procedure for the transformation of organoboranes to alkanes. 4-tert-Butylcatechol, a well-established radical inhibitor and antioxidant, is acting as a source of hydrogen atoms. An efficient chain reaction is observed due to the exceptional reactivity of phenoxyl radicals toward alkylboranes. The reaction has been applied to a wide range of organoboron derivatives such as B- alkylcatecholboranes, trialkylboranes, pinacolboronates, and alkylboronic acids. Furthermore, the so far elusive rate constants for the hydrogen transfer between secondary alkyl radical and catechol derivatives have been experimentally determined. Interestingly, they are less than 1 order of magnitude slower than that of tin hydride at 80 °C, making catechols particularly attractive for a wide range of transformations involving C-C bond formation.
- Villa, Giorgio,Povie, Guillaume,Renaud, Philippe
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supporting information; experimental part
p. 5913 - 5920
(2011/06/16)
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- 13C NMR spectral assignment of five epimeric 3α- versus 3β-functionalized cholestane pairs
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13C NMR chemical shift assignments of five α- and β-epimeric pairs of cholestanes functionalized at C-3 are presented. Empirical increment estimations proved to be a valuable tool for the unequivocal structural elucidation when compared with th
- Ramos,Santos,Almeida,Motherwell,Costa
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p. 861 - 863
(2007/10/03)
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- Nucleophilic Substitution Reactions of (Alkoxymethylene)dimethylammonium Chloride
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The use of imidate esters as potential replacements for diethyl azodicarboxylate and triphenylphosphine in the Mitsunobu reaction is described. A series of secondary alcohols were allowed to react with (chloromethylene)dimethylammonium chloride, generated from dimethylformamide (DMF) and oxalyl chloride, to give imidate esters. Reaction of these salts with potassium benzoate or potassium phthalimide gave the products of SN2 substitution in excellent yields with clean inversion of stereochemistry. Optimization of reaction conditions is discussed as a means to increase the atom economy of the process by minimizing the quantity of nucleophile required.
- Barrett, Anthony G. M.,Braddock, D. Christopher,James, Rachel A.,Koike, Nobuyuki,Procopiou, Panayiotis A.
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p. 6273 - 6280
(2007/10/03)
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- Oxidation of ethers to esters by photo-irradiation with benzil and oxygen
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A novel method for the conversion of ethers to esters by photo-oxidation using benzil and molecular oxygen, and its plausible reaction mechanism participated by benzoylperoxy radical are described.
- Seto, Hideharu,Yoshida, Keigo,Yoshida, Shigeo,Shimizu, Takeshi,Seki, Hiroshi,Hoshino, Mikio
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p. 4179 - 4182
(2007/10/03)
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- Nucleophilic Substitution of (Alkoxymethylene)dimethylammonium Chloride with Carboxylate Salts: a Convenient Procedure for the Synthesis of Esters with Inversion of Configuration
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Secondary alcohols are converted into benzoate esters with inversion of configuration via sequential reaction with (chloromethylene)dimethylammonium chloride and potassium benzoate.
- Barrett, Anthony G. M.,Koike, Nobuyuki,Procopiou, Panayiotis A.
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p. 1403 - 1404
(2007/10/02)
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- Efficacious modification of the Mitsunobu reaction for inversions of sterically hindered secondary alcohols
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A practical modification of the Mitsunobu protocol for effecting stereochemical inversions of alcohols has been discovered in which use of p-nitrobenzoic acid as the nucleophilic partner results in significantly improved yields with relatively hindered su
- Martin,Dodge
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p. 3017 - 3020
(2007/10/02)
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- The Use of a Phosphine Containing a Basic Group in the Mitsunobu Esterification Reaction
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Use of diphenyl(2-pyridyl)phosphine instead of triphenylphosphine in the Mitsunobu esterification reaction facilitates isolation of the desired ester.The resulting phosphine oxide is readily removed by a dilute acid wash. 31P n.m.r. investigations of the
- Camp, David,Jenkins, Ian D.
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p. 1835 - 1839
(2007/10/02)
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- POLYMER-SUPPORTED PHOSPHINE-HALOGEN COMPLEXES - 2 A NEW FACILE WAY FOR ESTERIFICATION OF CARBOXYLIC ACIDS
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The easily available complexes of polystyryl diphenyl phosphine with halogens are convenient condensating agents in the esterification of carboxylic acids under very mild conditions.The isolation of the ester by a simple filtration and evaporation process is a further interesting feature of this reaction.
- Caputo, Romualdo,Corrado, Elvira,Ferreri, Carla,Palumbo, Giovanni
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p. 1081 - 1088
(2007/10/02)
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- Oxidation process using tellurium oxide catalysts
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The present invention relates to the use of telluroxides as mild and selective oxidizing agents serving to oxidize certain functions, notably >C=S groups, in the presence of other relatively easily oxidized functions which remain unaffected; telluroxides of interest as oxidizing agents include, for example, compounds of the formula: STR1 wherein R and R1, which may be the same or different, each represent an optionally substituted aryl or heterocyclic group; or R and R1 together with the tellurium atom therebetween represent a heterocyclic ring, which may contain one or more further heteroatoms, and which may carry substituents and/or fused aromatic rings.
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- OXIDATION OF BENZYL ETHER TO BENZOATE BY OZONE
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Ozoniation of benzyl ethers at low temperatures in acetone or methanol solvent smoothly gave the corresponding benzoates in good yields.
- Hirama, Masahiro,Shimizu, Mitsuaki
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p. 781 - 786
(2007/10/02)
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- Reactions of Relevance to the Chemistry of Aminoglycoside Antibiotics. Part 13. A Novel Synthesis of Benzyl Ethers
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Benzyl ethers were prepared from alcohols by reaction with chloro(phenylmethyl)dimethylammonium chloride and sodium hydrogen telluride in sequence.The salt (1) 1)OR2Cl-; R1=H, R2=cholest-5-en-3β-yl> and sodium borohydride gave the borane complex of 3β-dimethylaminomethoxycholest-5-ene.Salt (1; R1=Ph, R2=cholest-5-en-3β-yl or 5α-cholestan-3β-yl) and ammonia or hydrazine gave the steroidal benzimidates or benzhydrazonate.
- Barrett, Anthony G. M.,Read, Roger W.,Barton, Derek H. R.
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p. 2184 - 2190
(2007/10/02)
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- Conversion of Thiocarbonyl Compounds into their Corresponding Oxo-derivatives using Benzeneseleninic Anhydride
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A series of thiocarbonyl compounds including xanthates, thioesters, thioureas, thiocarbonates, and thiones have been converted into their oxo-analogues by treatment with benzeneseleninic anhydride in tetrahydrofuran at room temperature.Except for readily enolised thiones where further oxidation can take place, the method works well and compares favourably with other literature procedures.One example of a selenocarbonyl ester was likewise converted efficiently into the corresponding ester.
- Cussans, Nigel J.,Ley, Steven V.,Barton, Derek H. R.
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p. 1650 - 1653
(2007/10/02)
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