Imides from amides

Give off ammonia freely when treated with aqueous NaOH solution in the cold (distinction from amides, imides and nitriles). 

The reaction is applicable to the preparation of amines from amides of aliphatic aromatic, aryl-aliphatic and heterocyclic acids. A further example is given in Section IV,170 in connexion with the preparation of anthranilic acid from phthal-imide. It may be mentioned that for aliphatic monoamides containing more than eight carbon atoms aqueous alkaline hypohalite gives poor yields of the amines. Good results are obtained by treatment of the amide (C > 8) in methanol with sodium methoxide and bromine, followed by hydrolysis of the resulting N-alkyl methyl carbamate ... 

Imides (e.g. phthalimide) can be purified by conversion to their potassium salts by reaction in ethanol with ethanolic potassium hydroxide. Hie imides are regenerated when the salts are hydrolysed with dilute acid. Like amides, imides readily crystallise from alcohols and, in some cases (e.g. quinolinic imide), from glacial acetic acid. 

Besides the technical method starting from naphthalene, phthalic acid and its substituted derivatives can be prepared by oxidation of o-xylene to phthalic acid with potassium permanganate. This compound can be subsequently transformed via an anhydride, imide, and amide to a derivative of phthalonitrile, which is the more convenient starting material for several coordination compounds. The synthesis of the ferf-butyl-substituted dicarbonitrile, which is a very common starting material for highly soluble phthalocyanines, is shown below.97,105... 

The use of the triphenylphosphine-carbon tetrachloride adduct for dehydration reactions appears to be a very simple way of synthesizing nitriles from amides, carbodi-imides from ureas, and isocyanides from monosubstituted formamides. All of these reactions involve the simultaneous addition of triphenylphosphine, carbon tetrachloride, and tri-ethylamine to the compound to be dehydrated. The elimination of the elements of water is stepwise. An adduct, e.g. (46), is first formed, chloroform being eliminated, which decomposes to produce hydrogen chloride and the dehydrated product. 

The problem of the nucleophilicity of amides in glycosylation reactions is not limited to the sulfoxide method and has been shown to result in the formation of glycosyl imidates from intermolecular reaction with activated donors. It appears that this problem may be suppressed by the prior silylation of the amide [348,349]. Accordingly, it may be sufficient to operate the sulfoxide method with an excess of triflic anhydride when amides are present so as to convert all amides into O-triflyl imidates, which are then hydrolyzed on work-up. Despite these problems, several examples have been published of successful sulfoxide glycosylation reactions with acceptors carrying remote peptide bonds [344,345] and with donors coupled to resins via amide-based linkages [346,347], with no apparent problems reported. Sulfonamides and tertiary amides appear to be well tolerated by the sulfoxide method [340,350],... 

Another approach to reduction of an amide group in the presence of more easily reduced groups is to convert the amide to a more reactive species. One such method is conversion of the amide to an O-alkyl imidate with a positive charge on nitrogen.63 This method has proven successful for tertiary and secondary, but not primary, amides. Other compounds which can be readily derived from amides and that are more reactive than amides toward hydride reducing agents are a-alkylthioimmonium ions64 and a-chloroim-monium ions.65... 

The chemistry of imidates and their methods of synthesis have been reviewed [32], Imidates are mainly available via the Pinner synthesis, via iminochlorides, from amides, from aldehydes and ketones, and via unsaturated systems [32]. 

The hydrolysis of imidate salts is a technique to generate in situ hemi-orthoamide tetrahedral intermediates (44), and to observe their breakdown to yield the reaction products under kinetically controlled conditions. Such conditions can be ascertained by verifying that the reaction products are not ihterconverted (amide + alcohol ester +amine) during the reaction. This technique can therefore be used to test the principle of stereoelec-tronic control in the cleavage of tetrahedral intermediates derived from amides. 

Solubility was enhanced by the presence of meta and ortho isomer links in the diamine portion of the molecule. Ttie polymers prepared with 3,3 -ODA and 2,4 -ODA were found to be readily soluble at 30-40% solids at room temperature in amide solvents. These polyimides are also readily soluble in low-boiling chlorinated solvents. They can therefore be spray-coated onto desired substrates in the fully-imidized form and thus eliminate the need for taking the substrate to elevated temperatures. Hiese soluble phenoxy-linked polyimides yield tough, flexible, colorless to pale yellow transparent films from amide or cholorinated solvents. Their potential for use in electronic applications should be excellent. 

Khoee S, Zamani S (2007) Synthesis, characterization and fluorimetric studies of novel photoactive poly(amide-imide) from anthracene 9-carboxaldehyde and 4,40-diaminodiphenyl ether by microwave irradiation. Eur Polym J 43 2096-2110... 

The photolytic cleavage of alkyl aryl sulfoxides has been shown to occur via initial C—S bond homolysis, in accordance with the common mechanistic assumption. Secondary and tertiary alkyl groups show high chemoselectivity for alkyl C—S cleavage. Uniquely, alkene products have been isolated, formed by disproportionation of the initial alkyl radical, with the formation of benzaldehyde and racemization of primary alkyl compounds. An investigation into the photochemical conversion of N-propylsulfobenzoic imides into amides in various solvents revealed a solvent dependence of the observed mechanism. In ethanol, sulfur dioxide extension forms a biradical which abstracts a hydrogen atom from the solvent, whereas in aromatic solvents biradical formation by a single electron transfer is implicated. The photolysis and thermolysis of l,9-bis(alkylthio)dibenzothiophenes and /7-aminophenyl disulfide have been studied. 

For insulating polymers, a local activation can be achieved by appropriate laser light. Cleavage of chemical bonds is followed by local electronic conductivity and the possibility of metal ion discharge. Another type of activation is the light-induced polyimide transformation from imide to amide producing free electrons [6.132]. 

With the powerful formylation reagent IV -diformylacetamide imides are obtained from amides or lactams in good yield (equation 56). Oxidation reactions also have found some application in the synthesis of imides. For example, catalytic amounts of ruthenium tetroxide and 10% aqueous NaI04 as cooxidant in an optimized reaction medium (ethyl acetate-water) oxidize acyclic amides to imides. The reaction rate is inversely related to the electron-withdrawing power of the acyl group, i.e. the electron density at the nitrogen atom (equation 57). 

JHC1757). The reverse order of the reaction steps can also be used an imidate or amide is initially formed from nitrile 30 and then these intermediates are transformed into compounds 80 upon treatment with NaSH (1986JHC1757, 1988JPR585). 

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