Cycloaddition reactions of some analogs of the acridizinium ion

Abstract

Abstract The 1‐aryl‐2‐imidazo[1,2‐ b ]isoquinolin‐4‐ium system ( 3 and 4 ), prepared by the action of aniline, or a suitable aniline derivative upon 2‐phenacyl‐3‐chloroisoquinolinium bromide undergoes cycloaddition reactions only with the more nucleophilic alkenes such as cyclopentadiene or 9‐vinylcarbazole. The pyrazino[1,2‐ b ]isoquinolin‐5‐ium‐2‐oxide ( 8–10 ) system reacts with nucleophilic alkenes more readily than does the acridizinium system 1. For both systems the cycloaddition appears to occur across the meso position of the central ring.