Abstract
2-Aryl-hydrazononitriles 3a, 3b, 3c were prepared by coupling 3-ethylthio-5-cyanomethyl-4-phenyl-1,2,4-triazole (1) with diazonium salts 2a, 2b, 2c. Reacting 3a, 3b, 3c with both ethyl bromoacetate (4a) and 4-bromobenzyl bromide (4b) in DMF, in the presence of K2CO3, at 80 degrees C for 3-4h, gave the corresponding 4-amino-pyrazoles 6a, 6b, 6c, 6d, 6e, 6f. Diazotization of 6a, 6b, 6c, 6d, 6e, 6f, followed by reaction with NaN3, leads to the formation of 4-azidopyrazoles 8a, 8b, 8c, 8d, 8e, 8f, a new heterocyclic ring system. Interestingly, fusion of 4-azidopyrazoles 8d, 8e, 8f at temperature higher than their melting points with 5 degrees C for 2min did not give the expected fused pyrazolo[4,3-c]isoxazoles 9 but furnished instead the novel pyrazolo[4,3-b]quinolinones 10a, 10b, 10c, in high yields.