Amide from carboxylic acids

The same reagents can be used to form amides from carboxylic acids and amines, a method which is applicable to peptide synthesis. Condensation of A-benzyloxycarbonyl-L-phenylalanine and ethyl glycinate hydrochloride gave an 85% yield of purified dipeptide. 

In 2001, De Luca and GiacomeUi " reported a new simple and high-yielding one-flask synthesis of Weinreb amides from carboxylic acids and A-protected amino acids that uses different 1,3,5-triazine derivatives (such as 236) as the coupling agents (Scheme 104). The method allows the preparation of Weinreb amides 237 and hydroxamates as O-benzyl and 0-silyl hydroxamates that can be easily transformed into hydroxamic acids. 

Formation of amides from carboxylic acid derivatives already has been discussed in some detail (Section 23-9A) ... 

Related Methods Amides from Carboxylic Acids (Section 77) Protection of Amines (Section 105A)... 

The ammonolysis of acyl chlorides is commonly employed whenever the preparation of an amide is desired for the identification of a carboxylic acid. The acyl chloride is prepared and treated with aqueous ammonia, or, if the amide is very soluble in water, with ammonia in benzene. In the latter case the ammonium chloride is filtered off, and the amide obtained by evaporation of the benzene with powdered ammonium carbonate. The preparation of amides from carboxylic acids is based upon the formation of an equilibrium mixture when the ammonium salts of the acid are heated ... 

The coupling reagents EEDQ and permit the formation of amides from carboxylic acids... 

Desulfurization conditions applied to 1,4-dithiins may also cause reactions at other functional groups, such as formation of amides from carboxylic acids in the presence of SOCI2 and aniline [64LA(679)118], introduction of a formyl group under Vilsmeier conditions (54JA4960), or the formation... 

In conjunction with proton sponge, the activated phosphate 256 turned out to be an effective reagent in the direct synthesis of peptides and branched amides from carboxylic acids (equation 21). In this process, diamine 1 surpassed in its efficiency for such bases as triethylamine, V,iV-dimethylaniline, 2,6-lutidine and Hiinig bases225. 

Carboxylic acid amides from carboxylic acids... 

Carboxylic acid amides from carboxylic acid bromides s. 4, 430 COBr —> CONHs... 

The cyclocondensation of 4-alkoxy-l,l,l-trichloro-3-alken-2-ones with hydroxyl-amine using toluene as solvent is more efficient under the action of microwave irradiation than using the classical method (the average time ratio for the two methods is 1 160) [49]. Katritzky et al. have demonstrated the applicability of microwaves to the synthesis of a variety of 2-oxazolines from readily available N-acylbenzotriazoles and 2-amino-2-methyl-l-propanol under mild conditions (80 °C) with short reaction times (12 min). Use of N-acyl benzotriazoles also avoids some complications in microwave reactions, for example dimerization or the exclusive formation of amides from carboxylic acids [50]. 

Amides from Carboxylic Acids Peptide Synthesis. Analogous to ester formation, reaction of equimolar amounts of a carboxylic acid and (1) in THF, DMF, or chloroform, followed by addition of an amine, allows amide bond formation. The method has been applied to peptide synthesis (eq 5). One equivalent of (1) is added to a 1M solution of an acylamino acid in THF, followed after 1 h by the desired amino acid or peptide ester. The amino acid ester hydrochloride may be used directly instead of the free amino acid ester. An aqueous solution of the amino acid salt can even be used, but yields are lower. 

Catalytic Effect of Carbon Dioxide in Amidation Reactions using CDL 1 is widely used in the formation of amides from carboxylic acids and amines. It was found that when the CO2 released in the acylimidazole formation step was thoroughly removed from the reaction vessel, by means of better agitation and ventilation, the amidation became substantially slower. Further investigation confirmed the catalytic effect of CO2 in amidation... 

Triphenyl phosphine, mercuric chloride, disulfide Subst. carboxylic acid amides from carboxylic acids Redoxidative peptide synthesis... 

Without additional reagents Reactions with tris(dialkylamino)boranes Carboxylic acid amides from carboxylic acids Enamines from ketones... 

Sodium hypochlorite N Chloroearboxylie acid amides from carboxylic acid amides... 

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