Arylcarboxylic acids

Preparation of Arylcarboxylic Acids and Derivatives. The general Friedel-Crafts acylation principle can be successfully appHed to the preparation of aromatic carboxyUc acids. Carbonyl haUdes (phosgene, carbonyl chloride fluoride, or carbonyl fluoride) [353-50-4] are diacyl haUdes of carbonic acid. Phosgene [75-44-5] or oxalyl chloride [79-37-8] react with aromatic hydrocarbons to give aroyl chlorides that yield acids on hydrolysis (133) ... 

Cobalt bromide is used as a catalyst in the technology of production of arylcarboxylic acids by the oxidation of methylaromatic hydrocarbons (toluene, p-xylene, o-xylene, polymethyl-benzenes). A cobalt bromide catalyst is a mixture of cobaltous and bromide salts in the presence of which hydrocarbons are oxidized with dioxygen. Acetic acid or a mixture of carboxylic acids serves as the solvent. The catalyst was discovered as early as in the 1950s, and the mechanism of catalysis was studied by many researchers [195-214],... 

An alternative mechanism [8] entails reaction of cyanamide (or dicyandiamide) with the dye phosphonate to give an O-acylisourea derivative (7.47). This is able to react directly with cellulose to form dye-fibre bonds, urea being released as the anticipated by-product (Scheme 7.31). In support of this mechanism, it is known that O-acylisourea derivatives of arylcarboxylic acids react readily with alcohols and this constitutes an efficient route for the preparation of carboxylic esters [44]. 

G. Prakash, G. K. S. Efficient Chemoselective Carboxylation of Aromatics to Arylcarboxylic Acids with Superelectrophilically Activated Carbon Dioxide-Al2CI6/Al System. J. Am. Chem. Soc. 2002, 124, 11379-11391. (d) Klumpp, D. A. Rendy, R. McElrea, A. Superacid Catalyzed Ring-opening Reactions Involving 2-Oxazolines and the Role of Superelectrophilic Intermediates. Tetrahedron Lett. 2004, 45, 7959-7961. 

In 2006, Ukai et al. proposed an interesting alternative with a rhodium(I)-catalyzed carboxylation of aryl- and alkenylboronic esters proceeding under mild conditions, and leaving ancillary reactive functional groups such as carbonyl- and cyano unreacted [51] (Scheme 5.13). Considering that organoboronic esters are easily available, and that various functional groups are tolerated, this reaction appeared to be particularly useful for the preparation of functionalized arylcarboxylic acids, such as benzoic and cinnamic acid derivatives. 

When an alkyl aryl ketone is heated with yellow ammonium polysulphide solution at elevated temperature, an aryl-substituted aliphatic acid amide is formed the product actually isolated is the amide of the tu-arylcarboxylic acid together with a smaller amount of the corresponding ammonium salt of the carboxylic acid. 

Naturally, reactions are especially interesting to us if the products obtained are not readily accessible by the methods of classic organic chemistry but are easily preparable with our complexes. We found one such example upon treatment of pentacarbonyl[methoxy(aryl)carbene]chrom-ium(O) complexes with oxygen, sulfur, or selenium (76). In this way one obtains conveniently the corresponding methyl esters of arylcarboxylic acids and the O-methyl esters of arylthio- as well as arylselenocarboxylic acids this seems to us to be synthetically useful in the last two cases ... 

The reactivity of the a-methylene group in lactams allows Claisen condensation with esters of formic, oxalic, and arylcarboxylic acids. Treatment of ethyl formate with A-methylpiperidone, followed by acidification, yields a salt of 1 -methyl- J2-piperideine, whereas in an alkaline medium its dimer was isolated.34- 158 With oxalic acid ester as the condensing reagent, 1-methyl-J2-pyrroline-2-carboxylic acid159 and l-methyl-d2-piperideine-2-carboxylic acid160 were obtained (Scheme 4). 

Metal-promoted approaches have been investigated for the preparation of indazoles. A copper(II) oxide-catalyzed regioselective synthesis of 1-alkyl- and 1-aryi-1 //-indazoles 25 from ortho-halogenated alkanoylphenones, benzophenones, and arylcarboxylic acids 24 with hydrazines in the presence of potassium carbonate has been developed <07OL525>. A... 

Aiylcaiboxylic acids, A-dan.syl amino acids 2-Arylcarboxylic acids Halogen-substituted 2-aryloxypropionic acids Amino acid derivatives... 

Epileptic seizures in overdosed patients may indicate a degree of nervous system toxicity. Convulsions in poisoned patients are reported to be more hkely with mefenamic acid than with other compounds (1). Other nervous system reactions (such as headache) are less frequent than with the arylcarboxylic acid derivatives. Coma has also been described as a consequence of mefenamic acid overdosage (2). 

KMn04 can also dihydroxylate alkenes, particularly electron-poor ones. More electron-rich alkenes may be oxidized further to the dicarbonyl compound. KMn04 can also oxidize alkylbenzenes to the arylcarboxylic acids. The mechanism of the later reaction remains quite obscure. 

Ruthenium complexes catalyze the reaction of primary alcohols with o-phenylenediamine. The catalyst apparently has dual roles in promotion of cyclization and oxidation of the alcohol to aldehyde <91CL1275>. A novel palladium-catalyzed carbonylation of iodobenzene has been linked to base-induced coupling and cyclization with o-phenylenediamine to give 2-arylbenzimidazoles without having to use an arylcarboxylic acid (Scheme 152) <93JOC7016>. 

Henry found that arylpalladium salts react with carbon monoxide in hydroxylic solvents to form arylcarboxylic acids or their derivatives, depending upon the solvents 82). 

Arylcarboxylic acids.1 a-Lithiation of a tricarbonylchromium complex of an alkylarcne followed by reaction with C02 provides complexes of a-arylcarboxylic acids. 

Few studies refer to the oxidation of aromatics. The hydroxylation of benzene to phenol [81] and the oxidation of alkylaromatics to arylcarboxylic acids [82] have been claimed. The oxyfunctionalization of saturated C-H bonds has not been reported. 

Pyridyl substituents linked to benzimidazoles were prepared by the condensation of hetero arylcarboxylic acids 212 with 1,2-phenylenediamine in the presence of PPA. When the reaction mixtures were subjected to MWI for 2-4 min, imidazoles 213 215 were obtained in 61-97% yields (Scheme 45). Conventional heating gave comparable yields, but after a longer time (4-16h) and with twice the amount of PPA (03H1457). 

It is not necessary to use phosphorus oxychloride complexes of formamides, because Roh and Kochendorfer in 1937 demonstrated that the iminium chlorides themselves react similarly and Bosshard and Zollinger have shown that comparable yields can be obtained using chlorodimethylformiminium chloride as the reagent. However, in the synthesis of diarylketones good yields are only obtained when the phosphorus oxychloride complex of the corresponding arylcarboxylic acid amide has been used The synthesis of ketones from carboxylic acid amides, phosphorus oxychloride and suitable substrates predates the aldehyde synthesis by approximately 40 years but it is of only limited usefulness because side reactions are very often encountered... 

The reaction of arylcarboxylic acid hydrazides with phosphorus pentachloride is the classical method of synthesis of hydrazidoyl chlorides I... 

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