Carboxamides imino

Photooxidation of imino ether 540 in the presence of potassium cyanide led to the a-amino carboxamide 542, which could be transformed by simple reaction steps to 5-carboxamidoyohimbine (545) (271). 

New rearrangements of 2-imino-2//-l-benzopyran-3-carboxamides under the action of anthranilic acid as an N-nucleophile have been revealed. Depending on the conditions 2-(2-oxo-2//-l-benzopyran-2-yl)-3//-quinazolin-4-ones or 2-oxo-2//-l-benzo-pyran-3-((V-2-carboxyphenyl)carboxamides were found to be the products. 

The reaction of 2-imino-2/7-pyrano[2,3-c]pyridine-3-carboxamide with substituted 2-aminobenzophenones proceeds via ring opening and recyclization to give 3-(4-arylquinazolyn-2-yl)-277-pyrano[2,3-( ]pyridin-2-ones (Scheme 9) <2005SG1641>. 

The electrochemical oxidation of hypoxanthine (261) in aqueous solution gave the intermediate 6,8-dioxopurine (262), which is more easily oxidized than 261, leading to 6,8-dioxopurinediimine (263).408 It is proposed that the nucleophilic attack of water occurs at the 4- or 5-position of 263, leading to the imino alcohols 264 or 265 [Eq. (138)]. These two compounds decompose by subsequent chemical or electrochemical reactions to the three major final products 5-imino-2,4-imidazoledione, 5-hydroxyhydantoin-5-carboxamide, and 4-amino-4-carboxyimidazol-5-one. 

The previously unknown l,2,4-thiadiazole 4 oxides 64 were prepared by condensation of benzamidoximes or their derivatives with Appel salt (Scheme 4) <1996CC1273>. The reaction mechanism includes attack of the imino group in 65 on the S-l atom of the 1,2,3-clithiazole ring. The /V-oxidcs are shown to be the 4-isomers by analysis of the NMR and mass spectra of lsN-labeled and unlabeled products and X-ray structure determination of the derived carboxamide 66 <1999J(P1)2243>. 

Imino-6,7-dimethyl-5-oxo-l-phenethyl-1,2,5,6-tetrahydro-1,6-naphthyridine-3-carboxamide... 

The availability of amino-substituted furazans, both by direct synthesis from aminogly-oximes and via Hofmann degradation of the corresponding carboxamides, allows urea, thiourea, imino and acylamido derivatives, for example, to be prepared by reaction with isocyanates, isothiocyanates, aldehydes and acyl halides, respectively (73JPR791, 77JCS(P1)1616). Alkoxy and acyloxy derivatives are likewise formed from hydroxyfurazans (79JHC689). 

Preparation of A-(5- [(5- [(5- [(2- [amino(imino)methyl]amino ethyl)amino]-carbonyl -l-methyl-lH-pyrrol-3-yl)amino]carbonyl -l-methyl-lH-pyrrol-3-yl)amino]carbonyl -l-methyl-lH-pyrrol-3-yl)-4-[(2-bromoacryloyl)amino]-carbonyl-l-methyl-lH-pyrrole-2-carboxamide hydrochloride... 

Ethyl-/3-methylglutaric acid has been prepared by the acid hydrolysis of a,a -dicyano- S-ethyl-fl-methylglutarimide, 3-cy-ano-4-ethyl-6-imino-2-keto-4-methylpiperidine-5-carboxamide or the diimide of 8-ethyl- 9-methylpropane-a,a,a, a -tetracarboxylic acid by the oxidation of jS-ethyl-fl-methyl-5-valerolactone with chromic acid and by the reaction of sodium hypobromite on l,4-dimethyl-l-ethyl-3,S-cyclohexanedione. ... 

Imino-2-pyrazolin-4-carbonitriles and 4-carboxamides have been prepared by Taylor by reaction of hydrazines with malononitrile.1478... 

The imino-amine (51.6) reacts at room temperature with aldehydes or ketones with the formation of purines. The products obtained from aldehydes are slowly oxidized (by loss of two hydrogen atoms from the pyrimidine ring) at room temperature, but the ketone-derived purines are stable and are accompanied by smaller amounts of an imidazo[l,S-c]imidazoIe. During cyclization, the nitrile group is converted into a carboxamide. Pentane-2,4-dione, 2-furfuraldehyde and but-2-enal give the fully aromatized purine as the main or only product isolated (in 38-49% yield). Stirring an imino-nitrile for several hours or heating it for a few minutes with an anhydride converts it into a fused pyrimidine. 

The first step in the ring closure of carboxamide 107 (R=NH2) with imidates is the formation of an amidine intermediate, with subsequent nucleophilic attack of the imino group of the amidine on the carbonyl group this takes places with loss of the carboxamide iV-substituent [117]. This observation formed the basis of a simple synthesis of CHINOIN 143 enantiomers. From carboxamides 39 and 40 with ethyl m-chlorobenzimidate, 109 and 110 were obtained in high enantiomeric purity. The absolute configurations were determined by hydrolysis of 109 and 110 to the corresponding amino acid, which was identified by HPLC [79]. 

The iminyls (191), generated by oxidation of imino-oxyacetic acid derivatives of type (190) with persulphate, undergo intramolecular cyclization to 6-substituted phenanthridines (192) in yields of up to 78% (Scheme 78) N-methoxybiaryl-2-carboxamides undergo analogous cyclization to phenan-thridones, and triarylvinyliminyls similarly yield 2,3,4-triaryl-quinolines. 

Iron pentacarbonyl in boiling dibutyl ether converts primary thioamides to nitriles [47] in moderately good yields, for example, m-toluonitrile (66%), ben-zonitrile (64%). Reduction of a carboxamide by sodium borohydride requires fairly drastic conditions [48] but if the amide is first converted into the imino-ether by means of Meerwein s reagent and this is then treated with the reducing agent in ethanol at 60°, a good yield of the nitrile is obtained replacing the borohydride by sodium ethoxide raises the yield appreciably [49], for example, benzonitrile (95%), pentanenitrile (90%), 2,2-dimethylpropanenitrile (86%), diphenylacetonitrile (100%). 

Three proposals for the mechanism of metal-depending nitrile hydratases have been suggested, the most plausible assumes direct corrdination of the nitrile to the metal, which (by acting as Lewis-acid) increases the electrophilicity of the carbon atom to allow attack of a water-molecule. The hydroxy-imino-species thus formed tautomerizes to form the carboxamide [638-640]. 

New rearrangements of 2-imino-2//-l-benzopyran-3-carboxamides, on their treatment with anthranilic acid, have been revealed. 4-Quinazolinones (72) have been prepared by rearrangement of 4-imino-4//-3,l-benzoxazines (71) via amidine carboxamides, while dihydrothiazines such as (73) which are disubstituted at C(7) have been observed to undergo a cyclization-ring contraction reaction with substituted acrylic acids to yield pyrroles (74). This interesting transformation has been accounted for by the route outlined in Scheme 23. 

A similar transformation with iV-monosubstituted allenic carboxamides targeting lactams yields mixtures of imino dihydrofu-rans and the desired pyrrolidones whereas AgNOs-promoted cyclization of a-hydroxy allenes leads to 2,5-dihydrofurans, the same mild conditions allow conversion of allenyl ketones and aldehydes to their corresponding furan derivatives. A comparative overview concerning the reaction of these substrates with other metal salts or Lewis acid catalysts (HgClOa, PdCl2(MeCN)2, etc.) points out differences in product distribution. ... 

Exploratory experiments have shown that glycosylidene carbenes also insert into the N-H bond of sulfonamides, whereas carboxamides yield esters, as illustrated by the product obtained from an A-Boc-asparagine benzyl ester (Figure 7c) [32]. Presumably, such esters are formed by hydrolysis of the initially formed imino ether 0-glycosides, suggesting that glycosylidene diazirines may be used for (selective ) cleavage of peptidic bonds. 

SCHEME 2.115 Synthesis of 3-amino-5-(pyrrol-2-yl)isoxazoles from l-ethylthio-3-imino-pyrrolizine-2-carboxamides and hydroxylamine. 

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