Carboxylic acids coupling reactions

Imidazole-2-carboxylic acid, 4-methylr ethyl ester synthesis, 5, 474 Imidazole-4-carboxylic acid coupling, 5, 403 iodination, 5, 400 reactions... 

Haptens containing amino groups can be coupled directly to carriers containing carboxyl groups, or the amino group can be converted to a carboxylic acid by reaction with succinic anhydride. - When a keto or an aldehyde group is present in the hapten, it can be converted to a carboxyl via reaction with 0-(carboxymethyl)hydroxylamine or with hydrazides. Haptens containing double bonds can be made to react directly with mer-captoacetic or mercaptopropionic acid, or a two-step reaction may be performed bromination followed by reaction with mercaptocarboxylic acid. ... 

Esterification. Carboxylic acids react with (1) in CHCI3 or acetonitrile in the presence of 1 eq. of triethylamine to form an active ester (2), which can be isolated if desired. The esters (2) react with an alcohol, again in the presence of 1 eq. of base, to form an ester of the carboxylic acid. The reaction can be carried out in one step by mixing the acid, the alcohol, the coupling reagent, and 2 eq. of base in ether. In either case, the reaction takes place at 20°. Yields are generally in the range of 65-85%. 

Table 5.9 PA/PEST blends - blends containing a coupling agent copolymer formation by carboxylic acid + epoxide reaction ...

More recently, Osbom and Milstein reported the reactions of aryl chlorides with carbon monoxide and a base to form aromatic esters, and Alper reported related reactions of aryl chlorides in biphasic media to form carboxylic acids. The reaction of Milstein is shown in Equation 17.60, and the reactions of Osborn were conducted imder similar conditions with PCyj as ligand. These examples comprise some of the first coupling chemistry performed with aryl chlorides. 

The pme enantiomers can then be used in the construction of a final chiral liquid crystal or dopant. The chiral acid 141b can simply be esterified (Scheme 35) onto a simple mesogenic-like core (146) to provide a final chiral material (147). The ethyl ester can be reduced to the alcohol (145a) which can then either be esterified onto a carboxylic acid mesogenic core or, as shown in Scheme 36, be employed in a Mitsunobu etherification (DEAD reaction) to give aryl bromide 148, which is then involved in a conventional arylboronic acid coupling reaction to provide a final chiral liquid crystal (150) which has a particularly wide S range. 

An exception to the expected ester formation of a phenol and a carboxylic acid is found in the case of salicylaldehydes. Girard et al. found that salicylaldehydes (91) preferentially form hydrazones like 92 when DEAD or related azadicarboxylates are employed in the Mitsunobu reaction. The hydrazone formation occurs with or without a carboxylic acid coupling partner. If DEAD is used during the reaction, the neighboring alcohol is protected as the boc ester during the reaction. This presiunably occurs through Boc transfer from DEAD via a tetrahedral intermediate. The subsequent hydrazone formation can then proceed via a concerted or nonconcerted reaetion with the reactive triphenylphosphonium boc hydrazide species that is formed after the collapse of the tetrahedral intermediate. 

Additionally, functionalizations of C-H or N-H bonds to form carboxylic acids by reaction with CO2 were achieved using [(NHC)Cu] complexes. For example, Koboyashi has described a new access to isocoumarins by a multicomponent reaction that involves the coupling of an aryne, an alkyne and CO2 in the presence of a copper catalyst [eqn (11.2)]. ... 

Imtdazo[4,5-c]pyridtne, 4,5,6,7-tetrahydro-synthesis, 5, 623, 640, 641 Imidazo[4,5-c]pyridine-6-carboxylic acid, 4,5,6,7-tetrahydro-synthesis, 5, 623, 641 Imidazopyridines as anthelmintic, 1, 202 synthesis, 5, 462 Imidazo[l,2-n]pyridines deuterium exchange, 5, 611 diazo coupling, 5, 614 Dimroth rearrangement, 5, 613 halogenation, 5, 611 hydrogenation, 5, 614 Mannich reaction, 5, 612 nitration, 5, 612 1-oxides... 

Claisen ester condensation, 6, 279 Thiazolecarboxylic acid chlorides reactions, 6, 279-280 Thiazolecarboxylic acid hydrazides synthesis, 6, 280 Thiazolecarboxylic acids acidity, 6, 279 decarboxylation, 6, 279 reactions, S, 92 6, 274 Thiazole-2-carboxylic acids decarboxylation, S, 92 Thiazole-4-carboxylic acids stability, S, 92 Thiazole-5-carboxylic acids decarboxylation, S, 92 Thiazole-4,5-dicarboxylic acid, 2-amino-diethyl ester reduction, 6, 279 Thiazole-4,5-dicarboxylic acids diethyl ester saponification, 6, 279 Thiazolediones diazo coupling, 5, 59 Thiazoles, 6, 235-331 ab initio calculations, 6, 236 acidity, S, 49 acylation, 6, 256 alkylation, S, 58, 73 6, 253, 256 analytical uses, 6, 328 antifogging agents... 

Electrolysis of carboxylic acid salts m solution causes decaboxyladve coupling similar to Kolbe reaction. Thus, eleclrolysis of 3,3,3-trifluoro-2-trifluoromethyl-propanoic acid in die presence of some of its potassium salt gives the corresponding fluoroalkane in a satisfactory yield [7d] (equation 67). 

The decarboxylation reactions of fluonnated carboxylic acids are similar to those of their nonfluonnated counterparts, but predictably many exceptions exist The oxidation of the potassium salts of perfluoro acids with potassium persulfate leads to decarboxylation and coupling [93] (equation 59)... 

Carbamates can be used as protective groups for amino acids to minimize racem-ization in peptide synthesis. Racemization occurs during the base-catalyzed coupling reaction of an A-protected, carboxyl-activated amino acid and takes place in the intermediate oxazolone that forms readily from an A-acyl-protected amino acid (R = alkyl, aryl) ... 

---