A- carboxylic acid amides

Amides. Although similar to esters in terms of being a functional derivative of a carboxylic acid, amides, unlike esters, are relatively metabolically stable. In general, amides are stable to acid- and base-catalyzed hydrolysis. This stability is related to the overlapping electron clouds within the amide functionality and the corresponding multiple resonance forms. Amidases are enzymes that can catalyze the hydrolysis of amides. Nevertheless, amides are much more stable than esters. 

An alternative to the azlactone procedure for the preparation of short-chain dehydropeptides 19 is offered by the direct condensation of an a-oxo acid 17 on heating with one equivalent of a carboxylic acid amide or by the treatment of an a-oxo acid 17 with a nitrile in the presence of dry HC1 gas (Scheme 6). If the former reaction proceeds with the condensation of two molecules of amide per molecule of a-oxo acid, then the corresponding a,a-bis(acylamino) aliphatic acid 18 is formed, which on warming with acetic acid results in partial deamidation with formation of the corresponding dehydropeptide 19. 

Liao et al. used a carboxylic acid amide functionalised carbene and a phosphane in a mixed NHC/phosphane palladium(II) catalyst [261]. The system shows the usual ligand exchange behaviour meaning that the PPhj ligand can be substituted by PCyj. This made it possible to study the influence of the phosphane ligand on the performance of the catalyst. In the Suzuki-Miyaura reaction between phenylboronic acid and p-chloroacetophenone, the yield changes dramatically. When PCyj is chosen as the phosphane ligand, then quantitative yield is observed (for both the saturated and unsaturated NHC), but in the case of PPhj the yield drops to 8% (unsaturated NHC) or even 4% (saturated NHC). When... 

Figure 4.39 A carboxylic acid amide functionalised imidazolium salt and its silver I) carbene...

Figure 4.40 Proposed mechanism for the POP of (L)-lactide by a silver(l) complex of a carboxylic acid amide functionalised carbene.

Figure 4.42 Synthesis of homoleptic palladium(ll) carbene complexes using a carboxylic acid amide functionalised NHC ligand.

A related reaction is the conversion of a carboxylic acid amide into the corresponding acid. Treatment of an acetylaldonamide with nitrogen tetroxide in acetic acid at 0° afforded the acetylaldonic acid in good yield. Another example is as follows ... 

We selected a novel approach to design a masked or blocked aliphatic diisocyanate based on the fact that 1,3-disubstituted ureas undergo facile thermal dissociation to produce an isocyanate and an amine derivative. ) In the dissociation of mono acyl and aroyl ureas an isocyanate and a carboxylic acid amide is simultaneously produced. If the urea group is part of a cyclic system both fragments are parts of the same molecule. 

The presence of electron withdrawing groups at the a position (R3) of the acrylate derivative increases the reactivity of the reagent toward conjugate addition, while substituents in the ( position (R4) tend to provide steric constraints that hinder carbon-carbon bond formation (Scheme 3). Of the various acrylate derivatives employed in these reactions, the most frequently used have electron withdrawing functionality such as a carboxylic acid, amide, ester, or nitrile group or a combination of these. Direct pyridone formation can be achieved primarily through the use of either a,(J acetylenic esters or acrylate derivatives with P substituents (Y = SR, OR, NR2) that eliminate under the reaction conditions. 

An amide has an NH2, NHR, or NR2 group in place of the OH group of a carboxylic acid. Amides are named by using the acid name, replacing oic acid or ic acid with amide. For acids ending with carboxylic acid, ylic acid is replaced with amide. ... 

Explanation. Benzamide—a carboxylic acid amide, essentially possesses very feeble amphoteric properties exclusively, by virtue of the fact that it rmdergoes hydrolysis to give the corresponding acid and ammonia as shown below ... 

Peptides (s. a. Carboxylic acid amides, subst., Peptoids)... 

Unlike esters, which can be prepared by acid-catalyzed condensation of an alcohol and a carboxylic acid, amides cannot be prepared by an acid-catalyzed condensation of an amine and a carboxylic acid. Why ... 

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