- Efficient Method for Aromatic-Aldehyde Oxidation by Cleavage of Their Hydrazones Catalysed by Trimethylsilanolate
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The reactions of hydrazones, derived from various aromatic aldehydes bound to Rink resin and hydrazines, with trimethylsilanolate have been studied. In this process, the aldehydes were oxidized to the corresponding carboxylic acids. The reaction was also tested with success in solution, with various aromatic aldehydes easily being oxidized in one pot via hydrazone formation and trimethylsilanolate treatment. A mechanism for the hydrazone cleavage is proposed. The reaction may be used as an alternative method for aldehyde oxidation with the selectivity complementary to that of currently used reactions.
- Burglova, Kristyna,Okorochenkov, Sergei,Budesinsky, Milos,Hlavac, Jan
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p. 389 - 396
(2017/01/24)
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- Facile and direct synthesis of symmetrical acid anhydrides using a newly prepared powerful and efficient mixed reagent
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An efficient mixed reagent for direct synthesis of symmetrical carboxylic anhydrides from carboxylic acids has been prepared. Carboxylic acids are converted to anhydrides using triphenylphosphine/ trichloroisocyanuric acid under mild reaction conditions at room temperature. Short reaction time, excellent yields of products, low cost, availability of reagents, simple experimental procedure, and easy work-up of the products are the main advantages of the presented method.
- Rouhi-Saadabad, Hamed,Akhlaghinia, Batool
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p. 479 - 485
(2015/01/30)
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- Decarboxylative cross-coupling of aryl tosylates with aromatic carboxylate salts
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(Figure Presented) A bimetallic copper/palladium catalyst system is disclosed that enables the use of tosylates as carbon electrophiles in decarboxylative coupling reactions. A variety of aromatic carboxylate salts, regardless of their substitution pattern, have been coupled with these inexpensive and readily available electrophiles to give the corresponding biaryl compounds in good yields (see scheme).
- Goossen, Luksa J.,Rodriguez, Nuria,Lange, Paul P.,Linder, Christophe
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supporting information; experimental part
p. 1111 - 1114
(2010/04/29)
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- Biaryl and aryl ketone synthesis via Pd-catalyzed decarboxylase coupling of carboxylate salts with aryl triflates
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A bimetallic catalyst system has been developed that for the first time allows the decarboxylative crosscoupling of aryl and acyl carboxylates with aryl triflates. In contrast to aryl halides, these electrophiles give rise to non-coordinating anions as byproducts, which do not interfere with the decarboxylation step that leads to the generation of the carbon nucleophilic crosscoupling partner. As a result, the scope of carboxylate substrates usable in this transformation was extended from ortho-substituted or otherwise activated derivatives to a broad range of ortho-, meta-, and para-substituted aromatic carboxylates. Two alternative protocols have been optimized, one involving heating the substrates in the presence of CuI/1,10- phenanthroline (10-15 mol %) and PdI2/phosphine (23 mol%) in NMP for 1-24 h, the other involving CuI/l,10-phenanthroline (615mol%) and PdBr2/Tol-BINAP (2 mol % ) in NMP using microwave heating for 5-10 min. While most products are accessible using standard heating, the use of microwave irradiation was found to be beneficial especially for the conversion of non-activated carboxylates with functionalized aryl triflates. The synthetic utility of the transformation is demonstrated with 48 examples showing the scope and limitations of both protocols. In mechanistic studies, the special role of microwave irradiation is elucidated, and further perspectives of decarboxylase crosscouplings are discussed.
- Goossen, Lukas J.,Linder, Christophe,Rodriguez, Nuria,Lange, Paul P.
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supporting information; experimental part
p. 9336 - 9349
(2010/04/03)
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- Decarboxylative biaryl synthesis from aromatic carboxylates and aryl triflates
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A new catalyst system, generated in situ from Cu2O, 1,10-phenanthroline, PdI2, and Tol-BINAP, for the first time allows the decarboxylative coupling of carboxylic acids with aryl triflates. In contrast to previous decarboxylative couplings that remained limited to certain activated carboxylates, e.g., ortho-substituted benzoates, this halide-free protocol is generally applicable to aromatic carboxylic acid salts regardless of their substitution pattern. Copyright
- Goossen, Lukas J.,Rodriguez, Nuria,Linder, Christophe
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supporting information; experimental part
p. 15248 - 15249
(2009/03/11)
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- A convenient method for the preparation of 4-aryloxyphenols
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A convenient method for the preparation of 4-aryloxyphenols via the homologation of preformed phenols is described. Condensation of various 4-substituted phenols with either 4-fluorobenzaldehyde (8) or 4-fluoroacetophenone (9) yielded the corresponding 4-aryl-oxybenzaldehydes, 10, and acetophenones, 11, in 70-93% yield. Baeyer-Villiger oxidation of these materials with 3-chloroperoxybenzoic acid (MCPBA) yielded the corresponding 4-formyloxy and 4-acetoxyphenyl ethers which were hydrolyzed without purification to the desired 4-aryloxyphenols 12 in 72-94% yield. Both 4-fluorobenzaldehyde (8) and 4-fluoroacetophenone (9) are synthetically equivalent to the a4 umpoled synthon 6. Extension of this methodology of the preparation of 4,4'-[arylbis(oxy)]bisphenols from aromatic diols is also described. Condensation of various aromatic diols with 8 or 9 yielded the corresponding 4,4'-[arylbis(oxy)]bisbenzaldehydes 15 and acetophenones 16 in 71-89% yield. Baeyer-Villiger oxidation of these compounds with MCPBA yielded the desired 4,4'-[arylbis(oxy)]bisphenyl bisformates 17 and bisacetates 18 in 67-84% yield. Hydrolysis of these compounds afforded the desired 4,4'-[arylbis(oxy)bisphenols 19 in 70-91% yield.
- Yeager,Schissel
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- The Autoxidation of Alkylnitroaromatic Compounds in Base-catalysed Phase-transfer Catalysis by Polyethylene Glycol under Ultrasonic Radiation
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The use of ultrasonic agitation in the base-catalysed autoxidation of alkylnitrobenzenes in polyethylene glycol phase-transfer systems changes reaction selectivity fron the usual dimeric products to the carboxylic acid.
- Neumann, Ronny,Sasson, Yoel
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p. 616 - 617
(2007/10/02)
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