Urethans carboxylic acid amides

The instability of primary nitramines in acidic solution means that the nitration of the parent amine with nitric acid or its mixtures is not a feasible route to these compounds. The hydrolysis of secondary nitramides is probably the single most important route to primary nitramines. Accordingly, primary nitramines are often prepared by an indirect four step route (1) acylation of a primary amine to an amide, (2) A-nitration to a secondary nitramide, (3) hydrolysis or ammonolysis with aqueous base and (4) subsequent acidification to release the free nitramine (Equation 5.17). Substrates used in these reactions include sulfonamides, carbamates (urethanes), ureas and carboxylic acid amides like acetamides and formamides etc. The nitration of amides and related compounds has been discussed in Section 5.5. 

Urethans from carboxylic acid amides Hofmann degradation CONHs —> NHCOOP... 

Vinylogs (Vinylogous) s. azolides, vinylogous carboxylic acid amides, -Dieckmann cyclization, -l,2-dithiole-3-thiones, -urethans, -... 

The reactivity of different isocyanates varies widely, and the most reactive NCO groups can react with almost any compound that contains an active hydrogen [1, 2, 16]. The reactivity of the nucleophilic groups also varies primary amines are more reactive towards NCO than primary alcohols, followed by water, secondary and tertiary alcohols, other urethanes, carboxylic acids, and carboxylic acid amides in that order [16]. The isocyanate will, of course, react with the water present in the EPI formulation to form amines followed by further reactions producing urea and biuret. The mechanism of this reaction is shown in Pig. 5. As can be seen from the reaction mechanism CO2 is a byproduct of this reaction. 

Carboxylic acid amides and urethans or carboxylic acid esters from acylureas... 

Urethans and N-chlorocarboxylic acid amides from carboxylic acid amides... 

Urethans from carboxylic acid amides Degradation with loss of 1 -atom... 

O-silyl ketene N,0-acetals 37,90s43 urethans, rearrangement 43,277 Carboxylic acid amides, N, N-disubst. 

Diphenyl phosphoryl azide in dimethylformamide followed by triethylamine added at or below 0° to a soln. of N-carbobenzoxy-L-leucyl-L-leucine and L-valyl-L-phenylalanine methyl ester hydrochloride in the same solvent, stirred several hrs. at the above temp, and overnight at room temp. -> product. Y 87%. - Practically no racemization occurred. F. e., also direct prepn. of urethans from carboxylic acids (cf. Synth. Meth. 17, 393) by a simplified Curtius degradation, s. T. Shioiri, K. Ninomiya, and S. Yamada, Am. Soc. 94, 6203 (1972) Tetrah. Let. 1973, 2343 synthesis of N-subst. carboxylic acid amides and peptides with diethyl phosphoryl cyanide s. Tetrah. Let. 1973, 1595 coupling reagents in peptide synthesis, review, s. Y. S. Klausner and M. Bodansky, Synthesis 1972, 453 review of peptide synthesis s. J. Meienhofer, Chem. Technol. 3, 242 (1973). 

The linker group is immobilized as a urethane to the amino-functionalized carrier (59). It facilitates the attachment of a variety of molecules such as alkyl halides, alcohols or amines bound as carboxylic acid esters and amides. 

Acid-like includes carboxylic acid, tetrazole, sulphonamide (ionizable NH) etc. Amide like includes (substituted) amide. Tetrazole, sulfonamide, etc. Ester-like includes tertiary amide (substituted, no NH) ureas, urethane, sulfonamide, etc. 

Nitramines show no basic properties whatever — indeed, primary nitramines have distinct acidic properties and can form salts with alkalis. Conversely, nitr-amides may be more strongly acidic than carboxylic acids, as, for example, nitro-urethane, which is a stronger acid than formic acid. 

Thioanalogs of ketones, acetals, carboxylic acids, esters, amides, ° isocyanates, " urethanes, and ureas are often prepared by reactions similar to those used for... 

The reaction of NCO groups and carboxylic acid groups resulted in the formation of amide linkages and carbon dioxide as blowing agent. This reaction has led to the invention of urethane foam preparation, and the polyurethane industry has become one of the biggest plastic industries. A model reaction of a polyamide foam formation is shown below ... 

Two different polyurethanes were used as starting materials a solid elastomer based on a trifunctional polyethertriol, 1,4-butanediol and methylenebis(phenyl isocyanate) and a flexible foam where the diol was replaced by water. The ammonolysis reactions were carried out at 139 °C and 140 atm for 120 min, and with a polyurethane/ammonia weight ratio of 1. Under these conditions the polyurethane conversion was practically total. The ammonolysis reaction transforms the CO group into urea and the ester groups and derivatives of carboxylic acids into amides, whereas ether and hydroxy groups are inert towards ammonia. Scheme 2.7 illustrates the stoichiometry proposed by the authors for the ammonolysis of the polyether urethane. 

When carboxylic acids (80) are exposed to 1 under microwave irradiation, mixed sulfocarboxy anhydrides (81) are formed. Subsequent treatment of the anhydrides with amines at elevated temperatures (microwave) yield acyl ureas (83) and amides (84). The ratio of the two products appears to be temperature controlled. For instance, when the anhydride 81 is exposed to primary or secondary amines at 150 °C, the acyl ureas are formed via the urethane 82. If 81 is exposed to primary or secondary amines at 80 °C, the corresponding amides are formed. 

Thus, as outlined in Scheme 4.4.9, a chloroformate-functionalised polystyrene resin 284 was treated individually with a wide range of anthranilic acid derivatives 285 in the presence of Hunig s base to give the urethane-linked system 286. Structurally diverse primary amines were readily coupled to the free carboxylic acid of 286 using standard PyBOP conditions to give anthranilamides 287. Thermal treatment of 287 caused the amide nitrogen to cyclise onto the... 

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