Transition‐Metal‐Free Synthesis of 2‐Substituted Benzo[cd]Indoles via the Reaction of 1‐Halo‐8‐lithionaphthalenes with Nitriles

Abstract

A simple and effective organolithium approach to the synthesis of 2‐substituted benzo[cd]indoles from peri‐dihalonaphthalenes and nitriles has been developed. The reaction proceeds via a surprisingly easy intramolecular aromatic nucleophilic substitution facilitated by the “clothespin effect”. The discovered transformation provides good isolated yields, allows usage of an extensive range of nitriles, and demonstrates a good substituents tolerance. UV‐absorption and NMR spectra of the obtained benzo[cd]indoles and their protonated forms demonstrated exclusive protonation to indole nitrogen atom even in the presence of two NMe2 groups in positions 5 and 6 (i.e. “proton sponge” moiety)