Synthesis of Dibenzoazulene Derivatives via Pd-Catalyzed (3+2) Alkyne Annulation of Dibenzosuberenone

Abstract

Non-benzenoid PAHs with pentagon/heptagon pairs have unique electronic structures and promising opto-electronic properties. However, the construction of pentagon/heptagon pair units in these PAHs is challenging. Herein, we developed a Pd-catalyzed (3+2) alkyne annulation reaction of heptagons, and constructed heptagon/pentagon pairs. The substrate scope is wide and the yield is good to moderate. A series of dibenzoauzlene derivatives were synthesized and their opto-electronic properties were systematically studied by UV-vis absorption and cyclic voltammetry. In addition, the dibenzoazulene derivative was further transformed to tropylium cation and tropyl radical, which showed bathochromic shifted absorption and switched aromaticity.