Spontaneous Cyclization of peri-Diiminonaphthalenes Leading to the Formation of Benzo[de]isoquinolines and Stable Benzo[de]isoquinoliniums

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

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 the indole nitrogen atom even in the presence of two NMe2 groups in positions 5 and 6 (i. e. "proton sponge" moiety).

N-2,6-Di(isopropyl)phenyl-2-azaphenalenyl radical cations

N-2,6-Di(isopropyl)phenyl-2-azaphenalenyl radical cations were obtained as a dark brown air-sensitive crystalline compound. The high HOMA values and the ACID calculation indicate relatively high aromatic character of a 5,8-di-tert-butyl derivative, and clean generation of a derivative without tert-butyl groups indicates that the di(isopropyl)phenyl group is sufficient for hampering the formation of the σ-dimer.