Decarboxylative homocoupling of (hetero)aromatic carboxylic acids

A variety of hetero(aromatic) carboxylic acids are shown to undergo decarboxylative homocoupling, mediated by a Pd/Ag system. This novel methodology for the synthesis of symmetrical biaryls avoids the use of haloarenes and organometallic compounds as starting materials.     

Decarboxylative reduction of free aliphatic carboxylic acids by photogenerated cation radical

The decarboxylation of free carboxylic acids was effected by a photogenerated cation radical of phenanthrene to yield the reduction product in the presence of a thiol, which provides an alternative method to the Barton decarboxylation procedure for aliphatic acids such as N-Boc amino acids.     

Cyclization of acetylenic derivatives of aromatic carboxylic acids

The Cu(I)-catalyzed intramolecular cyclization of 1-phenylethynyl-and 1-hexyn-1-yl-anthraquinone-2-carboxylic acid is a 6-endo-dig-addition, whereas the reaction for 1-(3-phenoxypropyn-1-yl)anthraquinone-2-carboxylic acid proceeds in a directionally nonspecific way. It is shown that the cyclization of vicinal acetylenic derivatives of aromatic carboxylic acids leads to the formation of the more stable of the possible cyclic structures.Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences, 630090 Novosibirsk. Novosibirsk State University, 630090 Novosibirsk. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2138–2146, September, 1992.     

Copper-catalyzed aerobic oxidative synthesis of aromatic carboxylic acids

A simple, practical and efficient copper-catalyzed method for synthesis of aromatic carboxylic acids has been developed. The protocol uses inexpensive CuI/L-proline as the catalyst/ligand, and readily available aryl halides and malononitrile as the starting materials, and the corresponding aromatic carboxylic acids were obtained in moderate to good yields. The method is of tolerance towards functional groups in the substrates.     

Decarboxylative bromination of α,β-unsaturated carboxylic acids via an anodic oxidation

A novel bromination of α,β-unsaturated carboxylic acids was developed via a decarboxylation by virtue of a direct anodic electro-oxidation.In this method,ammonium bromide was employed as a bromine source and the reaction features transition-metal-free,short time,and no additional supporting electrolyte.     

Cofluorescence of Eu in complexes of aromatic carboxylic acids

The fluorescence of Eu³⁺ in certain Eu³⁺–aromatic acid complexes were enhanced by over two orders of magnitude, by the addition of La³⁺; a process referred to as cofluorescence. Cofluorescence was observed only with certain aromatic acid ligands; trismesic acid, pyromellitic acid and mellitic acid; thereby clearly establishing a correlation between the structure of the ligand and the process of cofluorescence. While cofluorescence has been extensively studied using β-diketones as ligands, our studies demonstrate cofluorescence for the first time in ligands other than β-diketones. Furthermore, the mechanism of cofluorescence in the aromatic acid complexes studied by us appears to be different from that operating in the β-diketones. While intermolecular energy transfer is believed to occur in the β-diketones, formation of polynuclear complexes appears to be responsible for cofluorescence in the aromatic acid ligands.     

The optimized separation of aromatic carboxylic acids by HPLC

The optimization of the separation of eight aromatic carboxylic acids, using Hypersil SAS and MOS reverse phase columns, with respect to eluent (methanol : water) composition, pH, and temperature, is described. Window diagram techniques are used and the pH of the aqueous buffer and elution temperature are shown to be more critical than eluent composition.     

Copper-catalyzed synthesis of aromatic carboxylic acids from arylboronic acids and acetyl acetate

A simple and efficient copper-catalyzed method for the synthesis of aromatic carboxylic acids in moderate to high yields with great functional-group compatibility in the substrates has been developed. The new method uses readily available arylboronic acids and acetyl acetate as the starting materials and inexpensive CuI as the catalyst.     

Halogen-magnesium exchange on unprotected aromatic and heteroaromatic carboxylic acids

The magnesiation of halogenated aromatic and heteroaromatic carboxylic acids is accomplished by their treatment with MeMgCl in the presence of LiCl and subsequent reaction with i-PrMgCl.LiCl; the resulting double-magnesiated species react with a variety of electrophiles in up to 97% yield.     

Curtius rearrangement of aromatic carboxylic acids to access protected anilines and aromatic ureas

The reaction of a chloroformate or di-tert-butyl dicarbonate and sodium azide with an aromatic carboxylic acid produces the corresponding acyl azide, presumably through the formation of an azidoformate. The acyl azide undergoes a Curtius rearrangement to form an isocyanate derivative which is trapped either by an alkoxide or by an amine to form the aromatic carbamate or urea. The reaction conditions are compatible with a variety of functional groups and allow the synthesis of a number of aniline derivatives containing alkyl, halide, nitro, ketone, ether, and thioether substituents. [reaction: see text]     

Reaction of 4,6-dimethylpyrimidine with chlorides of aromatic carboxylic acids

The reaction of methyl groups with acyl chlorides is described for the first time in the pyrimidine series. The corresponding ketones — 6-methyl-4-phenacylpyrimidines — have been obtained from 4,6-dimethylpyrimidine and chlorides or aromatic carboxylic acids. A possible mechanism of the reaction is discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp, 1132–1135, August, 1973.     

Sodium borohydride reduction of aromatic carboxylic acids via methyl esters

A number of important aromatic carboxylic acids precursors, or intermediates in the syntheses of natural products, are converted into methyl esters and reduced to the corresponding primary alcohols using a sodium borohydride-THF-methanol system. The alcohols are obtained in 70–92% yields in 2–5 hours, in a pure state. This two-step procedure not only provides a better alternative to aluminum hydride reduction of acids but also allows the selective reduction of esters in presence of acids, amides, nitriles or nitro functions which are not affected under these conditions.     

Reactions of pyridoxal with aromatic carboxylic acids in alcoholic medium

Russian Journal of General Chemistry - Reactions of pyridoxal with benzoic acid and its derivatives in alcoholic medium afforded alkoxyfuropyridinium salts with potential biological activity.     

超高压液相色谱法分析12种氟苯甲酸示踪剂

建立了超高压液相色谱法测定12种新型水文示踪剂氟苯甲酸的分析方法。使用非极性固相萃取柱(200 mg,ENV+,6 mL)富集,Acquity BEH C18(50×2.1 mm.id.,1.7μm)超高压液相色谱柱、乙腈∶水(体积分数0.004%甲酸,pH 3.48)流动相、二极管阵列检测器,检测波长214 nm。方法相对标准偏差1.2%~4.2%,线性范围2.2~72.0μg/L(RSD:0.40%~1.6%)。平均回收率87.5%~111.6%之间(RSD 0.61%~9.8%.)。     

Copper(II) triflate-catalyzed reduction of carboxylic acids to alcohols and reductive etherification of carbonyl compounds

A protocol is described for the reduction of carboxylic acids to primary alcohols using 1,1,3,3-tetramethyldisiloxane (TMDS) and a catalytic amount of Cu(OTf)₂. Aliphatic as well as aromatic carboxylic acids are reduced in high selectivity and good yields. TMDS/Cu(OTf)₂ has also been found to be an efficient catalytic reducing system for the preparation of symmetrical ethers from carbonyl compounds under mild conditions.     

Studies of acylation kinetics of aspen wood with aromatic carboxylic acids

With the help of Erofeev-Kolmogorov and Eiring equations kinetic characteristics of acylation of the aspen wood with the aromatic carboxylic acids in presence of thionyl chloride in the trifluoroacetic acid medium were calculated and thermodynamic parameters of this process were established.     

Relationship between chromatographic properties of aromatic carboxylic acids and their structure

The retention of aromatic carboxylic acids and their esters in reversed-phase HPLC is proportional to the sum of their partition coefficients in octanol-water system and retention increments. This equation can be used for the identification of various side-products formed in monomer production.     

Selective esterification of non-conjugated carboxylic acids in the presence of conjugated or aromatic carboxylic acids over active carbon supported methanesulfonic acid

Non-conjugated carboxylic acids are selectively esterified in good yields in the presence of conjugated or aromatic carboxylic acids by stirring over active carbon supported methanesulfonic acid in di-chloromethane at room temperature.