Condensation of carboxylic acids

In a similar vein, condensation of carboxylic acid 123 with ethylenediamine leads to domazoline (124).29... 

N-Tosyl amides and lactams.2 DCC in combination with 4-pyrrolidinopyri-dine (4-PPy) effects condensation of carboxylic acids with secondary sulfonamides to provide N-tosyl amides in 75-90% yield. The intramolecular version of this reaction provides 4-, 5-, and 6-membered N-tosyl lactams in 60-90% yield. 

Metkoxycarbonyloxazoles. Condensation of carboxylic acids with methyl isocyanoacetate in the presence of K2C03 and DPPA (1 equiv.) leads to 5-substituted 4-methoxycarbonyloxazoles. Racemization is only slight when this C-acylation is applied to Boc-amino acids.1... 

Thiol esters.2 Condensation of carboxylic acids and thiols to form thiol esters can be effected with PPE in yields of 75-100%. 

Dihydrooxazoles are readily prepared from (V-acyl derivatives of /3-hydroxylamines by heating or by the action of thionyl chloride, sulfuric acid or phosphorus pentoxide (equation 167) (79JCS(P1)539>. The direct condensation of carboxylic acids with 13-hydroxylamines succeeds best with substituted compounds, such as norephedrine (equation 168). There are many variations of this general method, such as the use of imino ether hydrochlorides (equation 169) (78ACR375) and of cyanides (equation 170) (74LA996). 

Sharma et al. [13] synthesized the 2-oxazolines (iii) using the microwave assisted open vessel technique. The synthetic protocol involved the direct condensation of carboxylic acids with excess of 2-amino-2-methyl-l-propanol (i) at 170 °C. 

The special type of carbonyl-group derivatization is aimed for gas chromatography-mass spectrometry (GC-MS) determination of double-bond C = C positions in the unsaturated long-chain acids. The analytical derivatives for the solution of this problem are nitrogen-containing heterocycles. These compounds can be synthesized by condensation of carboxylic acids with 2-amino-2-methyl-l-propanol (2-substituted 4,4-dimethyloxazolines), 2-aminophenol (2-substituted benzoxazoles), and so forth. 

Dicyclohexylcarbodiimide has been used in the acylation of all common amino acids and is the most familiar condensation reagent in peptide chemistry, in spite of its skin-irritating and allergic properties. Outside peptide chemistry, dicyclohexylcarbodiimide has been used only infrequently for the condensation of carboxylic acids and amines, probably due to its high costs. 

A very simple procedure for the preparation of amidinium salts is the condensation of carboxylic acids with excess amine in the presence of POCb. Using this method, the selfcondensation reaction of amide-POCb adducts is suppressed. The salts are usually isolated as perchlorates (132 Scheme 14). In a related reaction benzoic acid is transformed by means of iVA( -dimethylethylenediamine and TiCU to the imidazolium chloride, which was separated as the PFe salt (133). 4... 

Ainsworth, C. The Condensation of Carboxylic Acid Hydrazides with Carbon... 

PhjSbO mediates the dehydrative condensation of carboxylic acids with amines via Ph3Sb(OCOR)2 as reactive intermediates [146]. This catalytic system has been applied to dipeptide synthesis (Scheme 14.73) [147]. Treatment of olefins with a mixture of AcOH and P4S10 in the presence of Ph jSbO affords alkylthio esters [148]. 

The direct condensation of carboxylic acids with aliphatic alcohols has been investigated by the use of fluorous ammonium salts as metal-free catalysts (Equation 4.24). Esterification reactions were carried out under mild fluorous biphasic conditions, in the presence of 1 mol% of fluorous ammonium triflate and without any water removal techniques. In the case of primary and secondary aliphatic alcohols, good to excellent ester yields were obtained. The fluorous ammonium triflate salt was easily recovered by simple phase separation and reused at least three times without any significant loss of activity [45],... 

Amide formation. o-Halophenylboronic acids catalyze the Diels-Alder reaction of acrylic acid as well as condensation of carboxylic acids with amines at room temperature (in the presence of 4A-molecular sieves). ... 

Amide synthesis. Limited amounts (0.35 equivalent) of the borane-dimethyl sulfide or THF complex promote condensation of carboxylic acids and amines. 

Amidation. Boric acid promotes condensation of carboxylic acids with amines by heating in toluene. ... 

Peroxycarboxylic acid esters are utilized as initiators for radical polymerization and are interesting intermediates for the decarboxylation of carboxylic acids. They are generally prepared by the acylation of hydro peroxides with acid chlorides, acid anhydrides, or imidazolides in the presence of a base. Condensation of carboxylic acids (20) with /-butyl-hydroperoxide (21) has been smoothly achieved by the use of diethyl phophorocyanidate and NEt3 under mild conditions giving f-butyl peroxycarboxylates (22) in good yield.9... 

Trifluorophenyl)boronic Acid-Catalyzed Amide Condensation of Carboxylic Acids and Amines N-Benzyl-4-phenylbutyramide. 

Many condensation polymers are copolymers, those consisting of two or more different repeat units. For example, condensation of carboxylic acid and amine monomers forms polyamides (nylons), whereas carboxylic acid and alcohol monomers form polyesters. 

Esters and amides. Condensation of carboxylic acids bearing an a-H with alcohols and amines proceeds via triacyloxybismuthines and ketenes under neutral conditions. 

This review covers the catalytic literature on condensation reactions to form ketones, by various routes. The focus is on newer developments from the past 15 years, although some older references are included to put the new work in context. Decarboxylative condensations of carboxylic acids and aldehydes, multistep aldol transformations, and condensations based on other functional groups such as boronic acids are considered. The composition of successful catalysts and the important process considerations are discussed. The treatment excludes enantioselective aldehyde and ketone additions requiring stoichiometric amounts of enol silyl ethers (Mukaiyama reaction) or other silyl enolates, and aldol condensations catalyzed by enzymes (aldolases) or catalytic antibodies with aldolase activity. It also excludes condensations catalyzed at ambient conditions or below by aqueous base. Recent reviews on these topics are those of Machajewski and Wong, Shibasaki and Sasai, and Lawrence. " The enzymatic condensations produce mainly polyhydroxyketones. The Mukaiyama and similar reactions require a Lewis acid or Lewis base as catalyst, and the protecting silyl ether or other group must be subsequently removed. However, in some recent work the silane concentrations have been reduced to catalytic amounts (or even zero) this work is discussed. 

Non-symmetric or symmetric ketones can be produced by the decarboxylative condensation of carboxylic acids. Rajadurai has also reviewed the process and possible reaction mechanisms. The general reaction is ... 

Kunishima M, Kawachi C, Hioki K, et al. Formation of carboxamides by direct condensation of carboxylic acids and amines in alcohols using a new alcohol- and water-soluhle condensing agent DMT-MM. Tetrahedron 57(8), 1551, 2001. 

HCHO with esters. This indicates that the condensation of carboxylic acids is easier than that of esters. 

Benzothiazoles can be synthesized by condensation of carboxylic acids with 2-aminothiophenol (Scheme 10.93) [181]. 

Other recent relevant developments have been the replacement of conventional acid catalysts with greener analogues. Direct esterification of carbo Q lic acids and alcohols continues to be a focus of attention. As examples, diphenylammonium triflate 8 and bulky diatylammonium sulfonates were shown to catalyse ester condensation of carboxylic acids and alcohols efficiently, and without the need for azeotropic water removal in the former case. Pentafluorophenylammonium triflate 9 was shown to be an efficient and cost-effective catalyst not only for esterification, but also for thioesterification, transesterification and macrolactone formation without requiring a dehydrating system. The superior catal)4ic efficiency of 9 relative to 8 was ascribed to the lower basicity of the pentafluoroaniline counter amine compared to diphenylamine. In related work, polyaniline... 

Murkute, A. D., Jackson, J. E. and Miller, D. J. 2011. Supported mesoporous solid base catalysts for condensation of carboxylic acids. J. Catal. 278(2) 189-199. 

In polypeptide chains, amino acids are joined together through the condensation of carboxylic acid and amine groups, leading to the formation of an amide or peptide bond (Figure 2b). A string of amino acids joined together in such a way is referred to as a polypeptide. Natural polypeptides are predominantly linear polymers and can... 

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