Carboxamides cyclization

Using triethyl orthoformate and 4(5)-(cyclohexylamino)imidazole-5(4)-carboxamide, cyclization to 3-cyclohexylhypoxanthine (7) was also accomplished. ... 

Amino-l-ribosylimidazole-4-carboxamide, cyclization of 78JHC353. Imidazole analogues of nucleic acid components 84MI5. Imidazole-bridged bimetallic center in Cu Zn superoxide dismutase and its... 

Carboxamides cyclize -aminopyridin-2-ones (II.I) on heating with zinc chloride under anhydrous conditions [3154]. A novel ring system was synthesized by warming the 3-amino-2-thioxothiazol-4-one (a rhodanine deriva-... 

An interesting subsequent reaction has been observed for a series of 1,1 -dial ky 1- 3 - but e ny 1 phenyl ketones the resulting unsaturated carboxamides cyclize to pyrrolidone derivatives ... 

Tetrahydro-l//,5//-pyrido[3,2,l-//]quinazoline-l,3-diones were prepared by the cyclization of l-tert-butoxycarbonyl-l,2,3,4-tetrahydroqui-noline-8-carboxamide on the action of 60% aqueous NaOH solution in THF at 50 °C (01M128). 

Tetraazaphthalocyanines are cyclization products of pyridine-2,3-dicarboni-triles,296-457 pyridine-2,3-dicarboxylic acid,459 or 2-cyanopyridine-3-carboxamide.295... 

Cyanopyridine-3-carboxamide when heated at 270—280 °C in the presence of magnesium yields a tetraazaphthalocyanine by cyclization. 

A new class of bicyclic oxalactam, 8-oxa-6-azabicyclo[3.2.1]octan-7-one 61 was synthesized by intramolecular cyclization of 3,4-dihydro-2H-pyran- 2-carboxamide 62 using p-toluenesulfonic acid as a catalyst in an equivalent mixture of DMF and benzene at 100 °C for 4 hours57, S8. Corresponding conversion of 3-cyclohexane carboxamide 63 to bicyclic lactam 64 has never been accomplished54. ... 

Partly saturated pyrazino[l,2-r-]pyrimidines were prepared by formation of the pyrazine ring. 2-Substituted-8-hydroxy-3,4-dihydro-177,277-pyrazino[l,2-r-]pyrimidin-l-ones were prepared by a [6+0] synthesis involving cyclization of 6-hydroxy-pyrimidine-4-(fV-hydroxyethyl)carboxamides <2005W02005/087766>. The 2/7-pyra-zino[l,2-c]pyrimidine-3-carboxamide 164 (Y = NH) was formed from [5+1] atom fragments via the uracil derivative 163 (Y = NH) and DMF-dimethyl acetal. Compounds 163 were prepared from 6-chloromethyluracil and glycine methyl ester 162 (Y = NH) (Scheme 20) <2004W02004/014354>. 

Intramolecular tandem cyclization of substituted piperidine-l-carboxamide 96 results in formation of cycloadduct 77 through the intermediary of A-sulfinylurea (Scheme 8) <2001JA8851, 2002JA3939>. 

Organoiron complexes (7) are converted in high yield into ammonium salts (8) these in turn undergo oxidatively induced ligand transfer and cyclization to give azetidinones (9) in moderate yields (Scheme 9). Formation of the trans product (9b) indicates a stereochemical sequence of trans addition to the olefin complex followed by carboxamidation with retention of configuration at the C—Fe bond. 

In a correction to previous work, the cyclization of 4-ureidobutyric acids with thionyl chloride has been shown (by NMR spectroscopy) to result in pyrrolidinone carboxamide derivatives and not aryl perhydro-l,3-diazepine-2,4-diones <00JHC111>. Optimization of the geometry of l-(o-nitrophenyl)-2-phenyl-l//-4,5,6,7-tetrahydro-l,3-diazepine has been undertaken using computer-based molecular modelling, and correlations made with theoretical and experimental UV spectra . 

Doyle s rhodium(n) carboxamidate complexes are undisputedly the best catalysts for enantioselective cyclizations of acceptor-substituted carbenoids derived from diazo esters and diazoacetamides, displaying outstanding regio- and stereocontrol.4 These carboxamidate catalysts consist of four classes of complexes pyrrolidinones... 

An interesting example of asymmetric induction has been used for the synthesis of (—)-l from L-tryptophan. Pictet-Spengler cyclization of the corresponding amide (127) with 5-chloropentanal afforded (—)-128 as the sole product. Removal of the unwanted carboxamide function was achieved in good yield by sodium borohydride reduction of die corresponding a-amino nitrile (—)-129, resulting in (—)-l (98). 

To this end, the diazoimidazole carboxamide compound 32 was transformed first by methylamine to the methyl-triazene derivative 39, which was reacted with 11 (". -phosgene to give the desired product 40 <2002JME5448>. In another approach, 32 was directly cyclized to the bicyclic product by using 1 C-labeled methyl isocyanate. This route allowed the synthesis of both the C-2-labeled 40 and the (7-methyl-labeled samples 41 <1997JLR371, 2002JME5448> (Scheme 13). 

Dilute solutions in aqueous buffers exposed to diffused or direct sunlight gave dimethylamine and 5-diazoimidazole-4-carboxamide (215). At pH 1.0 or pH 7.4 and above, this cyclized to 2-azahypoxanthine (216). In the intermediate pH range, a different product was obtained (217) which happens to be the aglycone of the antibiotic bredinin. Compound (217) was not formed by irradiation of (216). It was suggested that the betaine arose from a carbene (218) which had been quenched by water. However, (217) is colourless. Formulated injection solutions which had been found to lose activity contained 10 mg/ml... 

The cyclization of A-substituted-2-hydroxy-l-carboxamides with aldehydes and ketones has been successfully performed only in the case of N-methyl derivatives. Under similar conditions, the unchanged starting material was recovered from the reactions of other A-substituted-carboxamides (A-substituent = Ph, CH2Ph or CH2CH2Ph) [84JCS (Pl)2043]. 

Amino-l-carboxamides 288 (cis, n = 1, 2 tram, = 2 R = Ph, substituted aryl) were cyclized to dihydrouracils 289 with 1,1 -carbonyldiimidazole (CDI) with the retention of configuration (90T1943). The diexo-fused 290 was prepared by the same method (87T1921). 

The 2,3-disubstituted derivatives 316 are easily obtained by the cyclization of carboxamides 314 with orthoesters. 

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