Development of Heterocycle-Substituted and Fused Azulenes in the Last Decade (2010-2020).

Taku Shoji,Shunji Ito,Tetsuo Okujima

doi:10.3390/ijms21197087

Abstract

Azulene derivatives with heterocyclic moieties in the molecule have been synthesized for applications in materials science by taking advantage of their unique properties. These derivatives have been prepared by various methods, involving electrophilic substitution, condensation, cyclization, and transition metal-catalyzed cross-coupling reactions. Herein, we present the development of the synthetic methods, reactivities, and physical properties for the heterocycle-substituted and heterocycle-fused azulenes reported in the last decade.

Highlights

Azulene (1) is one of the 10π-electron non-benzenoid aromatic hydrocarbons having a fused structure of 5- and 7-membered rings
We summarize the preparation, reactivity, and physical properties of heterocycle-substituted and heterocycle-fused azulene derivatives that have been reported in the last decade
There are a wide variety of methods for their synthetic approach and the physical properties of the azulene derivatives are highly dependent on the type of heterocycles and their substitution and fused positions

Summary

Introduction

Azulene (1) is one of the 10π-electron non-benzenoid aromatic hydrocarbons having a fused structure of 5- and 7-membered rings. Resonance structure and numbering scheme of azulene (1). Due to their unique optical and electrochemical properties, heterocycle-substituted and heterocycle-fused azulene derivatives are expected to be applied to organic materials such as organic light-emitting diodes (OLEDs), organic field effect transistors (OFETs), solar cells, and biosensors. Several review articles on the classical heterocycle-substituted and heterocycle-fused azulene derivatives have been published so far [8,9,10,11,12,13,14,15,16,17]. We describe the development of heterocycle-substituted and heterocycle-fused azulene derivatives in the last decade. 2. Synthesis and Reactivity of Azulene Derivatives with 6-Membered Ring Heterocycles

Azulene Derivatives with N-Containing 6-Membered Heterocycles

Azulene Derivatives with N-Containing 5- and 6-Membered Heterocycles

Synthesis of Azulene-Fused Imide Derivatives

Findings

Conclusions