Synthesis of Linear Azolo and Pyrido Quinolines from Quinoline Derivatives

Angular N-tricyclic systems as triazolo[4,5-f]quinolines, triazolo[4,5-h]quinolines, imidazo[4,5-f]quinolines, imidazo[4,5- h]quinolines were in the past obtained by connection of either f or h sides of the quinoline ring and both the adjacent carbon atoms of five-membered rings containing nitrogen atoms. Several attempts at obtaining the corresponding linear N-tricycles were made in the last century, but only the angular derivatives were obtained. Since 2000 a new simple pathway, involving suitable quinoline derivatives, which afforded the linear azolo and pyrido quinolines (imidazo[4,5-g]quinolines, triazolo[4,5-g]quinolines and pyrido[2,3- g]quinoxalines) has been developed. Several linear N-tricyclic derivatives have shown some interesting pharmaceutical activity.