Synthesis of some derivatives of imidazo[1,2‐<i>a</i>]pyridine, pyrazolo[1,5‐<i>b</i>]imidazole, and 4‐(3<i>H</i>)quinazolinone from α‐ketohydrazidoyl bromides

Abstract

Abstract α‐Aroyl‐ N ‐arylhydrazidoyl bromides 1 react with 2‐aminopyridine in ethanol and give 2‐aryl‐3‐arylazo‐imidazo[1,2‐α]pyridines 2 in 60‐75% yield. The reaction of 1 with 3‐phenyl‐5‐aminopyrazole in ethanol leads to 2,6‐diaryl‐3‐arylazo‐1 H ‐pyrazolo[1,5‐ b ]imidazoles 3 in almost quantitative yield. Also, 1 react with anthran‐ilic acid in the presence of triethylamine giving 3‐arylamino‐2‐aroyl‐4‐(3 H )quinazolinones 4 in 80‐85% yield. The structures of the products were assigned and confirmed on the basis of their elemental analysis and electronic absorption, infrared and nmr spectra.