Electrophilic behavior of the pi delocalized azepinium ion: Friedel-Crafts reactions with benzenes and five-membered aromatic heterocycles

Abstract

[reaction: see text] Although the reactivity of tropylium ion with aromatic substrates is low, the reaction of azepinium ion with aromatic substrates such as benzene, phenol, furan, and thiophene resulted in the formation of 2-aryl-2H-azepine as a major product. An exceptional result in the formation of ring-contracted product was observed in the reaction with pyrrole.