Synthesis of dibenzo[a,f] quinolizinium and 2-phenyloxazolo [3,2-a] quinolinium perchlorates via acid-catalyzed cyclization of 1-(2-OXO-2-phenylethyl) quinolin-2(1H)-ones

摘要

Treatment of certain N-alkylated quinolin-2(1H)-ones with concentrated H_2SO_4 afforded oxazolo[3,2-a] quinolin-10-ylium perchlorates via a Z-form enol intermediate while others gave dibenzo[a,f] quinolizinium perchlorates via an E-form enol intermediate. We examined the structure of starting N-alkylated quinolin-2(1H)-ones and found that a methoxy group substituted at R_4 is required for the formation of tetracyclic dibenzo[a,f] quinolizinum perchlorates.