Azirines carboxamides

Azirine-3-carboxamides with a second substituent in the 3-position (599) were used by Nishikawa and Sato for the synthesis of dihydro-1,2,4-triazin-6-ones (600) (71JCS(C)2648). 

Thermal or photochemical treatment of isoxazoies 851 has been found to result in a ring-contraction reaction to produce acyl 277-azirines 852, which sometimes rearrange to form other heterocycles like oxazoles 853. This ring-contraction reaction can also be promoted by iron(ii) catalysts. Thus, 5-alkoxy- and 5-aminoisoxazoles isomerize to 27/-azirine-2-carboxylic esters and 2/7-azirine-2-carboxamides, respectively, in nearly quantitative yield by reaction with catalytic FeCb (Scheme 212) <1997T10911>. 

Aryl-27/-azirine-2-(/V-benzyl)carboxamides can be diastereoselectively reduced to the corresponding eu -aziridines using sodium borohydride11. The stereochemistry of the as-aziridines was revealed by H-NMR spectroscopy which showed a cis coupling constant of J2H,3h = 7-8 Hz. 

The analogous amines (356) were also studied and found to undergo reorganization to 2/f-azirine-2-carboxamides (358). Further heating of these compounds resulted in the isolation of pyrazine-2,5-dicarboxamides (361). The formation of 361 was suggested to proceed through either of the intermediate diradicals 358 or 359. ... 

The reduction of azirines with sodium borohydride to give the corresponding aziridines has been applied to a series of aziridine-2-carboxamides (259). The well established synthetic route of lithium aluminium hydride... 

A soln. of 3-p-dilorophenyl-2-phenyl-2H-azirine-2-carboxamide in methanol mixed with hydrazine hydrate, and refluxed 2 hrs. 3-p-dilorophenyl-5-phenyltetra-hydro-l,2,4-triazin-6-one. Y 36%. F. e. s. T. Nishiwaki and T. Saito, Soc. (C) 1971, 2648. 

A methanolic soln. of 2,3-diphenyl-2H-azirine-2-carboxamide mixed with hydroxyl-amine hydrodiloride and K-acetate in water, and the product isolated after 1 hr. 

A modification of this methodology allows the preparation of 3-(dialkylamino)-2H-azirines 10 from N,N-disubstituted carboxamides 9 [39] ... 

A mixture of 2,3-diphenyl-2H-azirine-2-carboxamide, NaBH4, and methanol refluxed 0.5 hr. 2,3-diphenylaziridine-2-carboxamide. Y 73%. F. e. and reagents s. T. Nishiwaki and F. Fujiyama, Synthesis 1972, 569. 

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