Amides, preparation reactions

Carboxyhc acids react with aryl isocyanates, at elevated temperatures to yield anhydrides. The anhydrides subsequently evolve carbon dioxide to yield amines at elevated temperatures (70—72). The aromatic amines are further converted into amides by reaction with excess anhydride. Ortho diacids, such as phthahc acid [88-99-3J, react with aryl isocyanates to yield the corresponding A/-aryl phthalimides (73). Reactions with carboxyhc acids are irreversible and commercially used to prepare polyamides and polyimides, two classes of high performance polymers for high temperature appHcations where chemical resistance is important. Base catalysis is recommended to reduce the formation of substituted urea by-products (74). 

Other Preparative Reactions. Polyamidation has been an active area of research for many years, and numerous methods have been developed for polyamide formation. The synthesis of polyamides has been extensively reviewed (54). In addition, many of the methods used to prepare simple amides are appHcable to polyamides (55,56). Polyamides of aromatic diamines and aUphatic diacids can also be made by the reaction of the corresponding aromatic diisocyanate and diacids (57). 

Polymerization of castor od, chemical or oxidative, results in higher viscosity or bodied ods that are more usehd in urethane coatings than the untreated castor od (87). Other castor derivatives used to prepare urethanes are amides prepared by reaction of castor od and alkanolamines, amides of ricinoleic acid with long-chain di- and triamines, and butanediol diricinoleate (88,89). 

The great reactivity of the sulfurane prepared by this procedure toward active hydrogen compounds, coupled with an indefinite shelf life in the absence of moisture, makes this compound a useful reagent for dehydrations,amide cleavage reactions, epoxide formation, sulfilimine syntheses, and certain oxidations and coupling reactions. 

Although Lehn and his coworkers prepared a large number of cryptands and derived complexes over the years, the synthetic approach to these compounds remained essentially similar for most of them. Details are presented for a number of such compounds in ref. 26. The essential features of these syntheses were use of amide-forming reactions in the absence of templating ions with reliance on a high dilution step to form the second ring. An alternative approach for the synthesis of cryptands was developed by Dye and his coworkers. Their approach involved the use of a flow synthesis to replace the high dilution step. 

Amides, prepared by condensation of tryptamine or substituted tryptamines with a large number of aliphatic, homocyclic, aromatic,and heterocyclic acids, have been used in the reaction. In few cases only did ring closure fail. ... 

The treatment of acyl halides with ammonia or amines is a very general reaction for the preparation of amides.The reaction is highly exothermic and must be carefully controlled, usually by cooling or dilution. Ammonia gives unsubstituted amides, primary amines give A-substituted amides, and secondary amines give N,N-disubstituted amides. Arylamines can be similarly acylated. In some cases aqueous... 

Preparation Of Thiol Acids, Thiol Esters And Amides By Reactions Of Carbonyl Sulfides With Grignard Reagents," Katritzky. A.R. Moutou, J.-L. Yang, Z. Org. Prep. Proceed. Int., 1995, 27, 361... 

Amides prepared from carboxylic acids and ammonia using CDI. Yields refer to reaction of the azolides with ammonia. 

Thiadiazoles have proven of some utility as aromatic nuclei for medicinal agents. For example, the previous volume detailed the preparation of a series of "azolamide" diuretic agents based on this class of heterocycle. It is thus of note that the 1,2,5-thiadiazole ring provides the nucleus for a clinically useful agent for treatment of hypertension which operates by an entirely different mechanism, p-adrenergic blockade. In its preparation, reaction of the amide-nitrile 211 with sulfur monochloride leads directly to the substituted thiadiazole 212. ... 

This preparation may be accomplished by using one molecular equivalent of lithium amide special reaction procedures must be employed, however, and the yields are not reproducible.2 The preparation may also be accomplished (with reduced yield) by using sodium amide, but only under special reaction conditions.3... 

Dehydration (cf., 6, 648). A reagent (1), prepared in situ from (C6H5),PO and Tf20 in the molar ratio 2 1, effects dehydration, usually at 25°, of amides or oximes to nitriles in >90% yield. It also effects condensation of acids and amines to form amides. The reaction of an aryl carboxylic acid with an o-phenylenediamine promoted by 1 provides 2-arylbenzimidazoles in >80% yield (equation I). If the... 

Amides prepared from both enantiomers of 10,10-dimethyl-4-aza-3-thiatricyclor5.2.1.01,5ldecane 3,3-dioxide (bornane-10,2-sultam) can be used in diastereoselective alkylation reactions to give high chemical yields and high diastereomeric ratios of monoalkylation products5,6,10,16-19. 

Analogously, thioacid fluorides can be used for the preparation of thioamides,114 and (difluoromethylcnc)amines can be aminated by metal amides.115116 Reaction of acid fluorides with imines leads to acyliminium compounds116 which can be further utilized, e g. in cycloaddition reactions.117 " 1 9... 

Synthesis from 1-pyridinio(arenethiocarbonyl)amidates and dimethyl acetylenedicarboxylate With the aim of preparing fused thiadiazepines, reactions of different l-pyridinio(arenethiocarbonyl)amidates 196 with dimethyl acetylenedicarboxylate 197 (DMAD) were conducted <1997JOC7788>. When an HCC13 solution of the amidates, prepared as described in Scheme 26, and DMAD was heated at 50-60 °C in a water bath for 8-11 h, products 198 were obtained and not the desired thiadiazepine (Scheme 27). 

Amides.1 Carboxylic acids can be converted directly into amides by reaction with a bis(dialkylamino)magnesium, prepared in situ by reaction of 2R2NH with n-butyl-sec-butylmagnesium (Alfa). 

Primary amines.2 A version of the Gabriel synthesis involves alkylation of the potassium amide prepared by reaction of 1 with KH. Yields are generally in the range of 60 to 90%. 

Amino acids exhibit chemical reactions that are typical of both amines and carboxylic acids. For example, the acid can be converted to an ester by the Fischer method. This reaction requires the use of an excess of acid because one equivalent is needed to react with the amino group of the product. As another example, the amine can be converted to an amide by reaction with acetic anhydride. Additional examples are provided by the reactions that are used in the preparation of peptides from amino acids described in Section 26.7 ... 

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