Flash vacuum pyrolysis of 1-azolyl-1-phenylhydrazono-2-propanones

Flash vacuum pyrolysis (FVP) of 1‐(2‐arylhydrazono)‐1‐(1H‐1,2,4‐triazol‐1‐yl)acetone 8a‐c at 650 °C and 2.67 Pa yielded 5‐substituted 1‐(1H‐indazol‐3‐yl)ethanone 14a‐c and 4,6‐disubstituted cinnoline 18a‐c. Similarly FVP of 1‐(1H‐benzo[d]imidazol‐1‐yl)‐1‐(2‐phenylhydrazono)acetone 9a‐c gave 8H‐benzo[4′,5′]imidazo[2′,1′:5,1]pyrrolo[2,3‐c]cinnoline derivatives 23a‐c. A plausible mechanism is suggested to account for their transformation based on the kinetics and products of reaction.