Ammonia with carboxylic esters

Although, the enzymatic reaction of esters with amines or ammonia have been well documented, the corresponding aminolysis with carboxylic acids are rarer, because of the tendency of the reactants to form unreactive salts. For this reason some different strategies have been used to avoid this problem. Normally, this reaction has been used for the preparation of amides of industrial interest, for instance, one of the most important amides used in the polymer industry like oleamide has been produced by enzymatic amidation of oleic acid with ammonia and CALB in different organic solvents [10]. 

As in 10-55 hydrazides and hydroxamic acids can be prepared from carboxylic esters, with hydrazine and hydroxylamine, respectively. Both hydrazine and hydroxylamine react more rapidly than ammonia or primary amines (the alpha effect, p. 445). Imidates, RC(=NH)OR, give amidines, RC(=NH)NH2. Lactones, when treated with ammonia or primary amines, give lactams. Lactams are also produced from y- and 5-amino esters in an internal example of this reaction. 

Other Gas Reactions. Several other reactive gases or vapours were examined but found to be unsatisfactory. No ester formation ( 1745 cm"1) was found when oxidatized films were exposed to acetic acid or formic acid vapour. Alcohol/carboxylic acid reactions in the solid state have often been suggested as the source of ester products, but not substantiated (4,5). Gaseous ammonia reacted with carboxylic acid groups to give absorptions at 1550 cm"1 [-C(=0)-0 ] and 1300 cm"1 (NHi +). However, these absorptions were very broad and the method inferior to acid measurement by SF. Although N20 did not react with oxidized polyolefins, the reaction of N02 with oxi-... 

Feuer and co-workers also nitrated ring-substituted toluenes to the corresponding arylnitromethanes with potassium amide in liquid ammonia. Sulfonate esters and NJ -dialkylamides undergo similar nitration the latter isolated as their a-bromo derivatives. Alkaline nitration of ethyl and ferf-butyl carboxylic esters with potassium amide in liquid ammonia yields both the a-nitroester and the corresponding nitroalkane from decarboxylation. ... 

The relative stability of the oxiranes to bases at room temperature allows the selective ammonolysis of carboxylic ester groups with ammonia in methanol,49 and, conversely, free hydroxyl groups may be esterified with acid chlorides or anhydrides in pyridine without affecting the oxirane ring. Hydroxyl groups may also be converted into alkyl ethers by using either the Haworth50 or the Purdie-Irvine procedure.5152... 

The teichoic acid shows an infrared absorption band at 1751 cm.-1, characteristic of carboxylic ester groups, which is not observed in samples from which the D-alanine residues have been removed. Removal of the u-alanine was readily effected with ammonia or hydroxylamine, when D-alaninamide or D-alanine hydroxamate were formed. The kinetics of the reaction with hydroxylamine reveal the high reactivity of its D-alanine ester linkages, which, like those in most other teichoic acids, are activated by the presence of a neighboring phosphate group. That the D-alanine residue is attached directly to the ribitol residues, instead of to the d-glucosyl substituents, was also shown by oxidation with periodate under controlled conditions of pH, when it was found that the D-alanine residues protect the ribitol residues from oxidation. Under the same conditions, all of the ribitol residues were oxidized in a sample of teichoic acid from which the D-alanine had been removed, and it is concluded that the ester groups are attached to C-2 or C-3 of the ribitol residues. 

Amides are very easily prepared by the interaction of carboxylic esters with concentrated aqueous ammonia (ammonolysis). 

Thus it appears that the starting methyl ester gg undergoes base-catalyzed cyclization to give the intermediate 12, which is opened by hydroxide attack at phosphorus to give lg. The desired diamide 9, formed either by direct hydrolysis of c or by opening of the intermediate 2 at the carbonyl carbon, loses ammonia with assistance from the free carboxylate to give li-... 

Many of the iV-alkyl and iV-aryl derivatives of urazine have been synthesized and characterized, but the parent substance is not well known. In the past, urazine has been prepared by thermal deammonation of carbohydrazide-iV-carboxamide [eq. (I)],1 fusion of hydrazidicarbamide with hydrazinium hydrogen sulfate [eq. (2)],2 fusion of earbohy-drazide with urea [eq. (3)],3 action of sodium hypobromite on semicarbazide [eq. (4)],4 reaction of dichlorourea with concentrated ammonia [eq. (5)],5 and the reaction between 1,2 hydrazine carboxylic ester and hydrazine hydrate... 

Using the principles we ve outlined above, you should be able to see how these compounds can be interconverted by substitution reactions with appropriate nucleophiles. We ve seen that acid chlorides react with carboxylic acids to give acid anhydrides, and with alcohols to give esters. They ll also react with amines (such as ammonia) to give amides. 

Bisoxadiazoles are formed from bis(mono)imido ester hydrochlorides and mono(bis)carboxylic acid hydrazides when the free ester is used, an amidrazone (27) is often formed which cyclizes with the elimination of ammonia to give 28.73 The reaction proceeds in the presence of higher boiling solvents or by mixing the reactants at a temperature higher than 100°, the imido esters forming first in the reaction mixture. The reaction of semicarbazide [Eq. (2), R = NH2] with imido esters does not, of course, lead to 2-amino-1,3,4-oxadiazoles but to the isomeric l,2,4-triazolin-3-ones.72 The reaction of N-substituted imidochlorides with aromatic acid hydrazides in the... 

Carboxylic amides. Gilman has extended the procedure of Corey et at. (2, 261) for oxidation of allylic alcohols to carboxylic esters to the preparation of carboxylic amides. Thus oxidation of aromatic and a,/ -unsaturated aldehydes with Mn02 in the presence of sodium cyanide and an amine gives the corresponding carboxylic amides in high yield. In the absence of sodium cyanide, high yields of nitriles are formed from aldehydes, ammonia, and manganese dioxide. 

Keto and carboxylic ester groups in side-chains are annulated by reaction with ammonia. In this example, the reactants are heated in molten ammonium acetate. 

In the previous Section 12.1 the formation of amides from the corresponding nitriles is well addressed. The latter method, the enzyme catalyzed reaction of carboxylic esters or acids with ammonia or amines yielding amides, has only recently been studied in depth. Encouraging results have been described, especially in the field of amidation of esters, a technology now being used by BASF to produce optically pure amines (vide infra). 

Reactions. As with other tertiary alcohols, esterification with carboxylic acids is difficult and esters are prepared with anhydrides (181), acid chlorides (182), or ketene (183). Ca.rba.mic esters may be prepared by treatment with an isocyanate (184) or with phosgene followed by ammonia or an amine (185). 

Acylation of nitrogen compounds by carboxylic esters. The action of carboxylic esters on ammonia or primary or secondary amines generally leads to carboxamides under relatively mild conditions, and the analogous treatment of carboxylic esters with hydrazine and hydroxylamine provides the most important methods of preparing simple carboxhydrazides and carbohydrox-amic acids. 

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