2-(2-Naphthyl)benzo[b]thiophen. Part IV. Further aspects of electrophilic substitution, and ring closures to yield pentacyclic derivatives

Abstract

Electrophilic reagents attack 2-(2-naphthyl)benzo[b]thiophen at the free position on the thiophen ring, but there does not seem to be any strongly preferred position for further electrophilic substitution. Attempts to decarboxylate 2-(1-nitro-2-naphthyl)benzo[b]thiophen-3-carboxylic acid produced internal nucleophilic displacement of the nitro-group to yield a pentacyclic lactone. A pentacyclic ketone and a pentacyclic phenol have been prepared by Friedel–Crafts ring closures between the benzo[b]thiophen and naphthalene ring systems. A direct synthesis of the title compound is reported.