Synthesis of benzo[d]imidazo[2,1-b]benzoselenoazoles: Cs2CO3-mediated cyclization of 1-(2-bromoaryl)benzimidazoles with selenium.

Mio Matsumura,Shuji Yasuike,Tadashi Hyodo,Yuki Murata,Yoshitaka Kanazawa,Arisa Yamauchi,Yuki Kitamura,Kentaro Yamaguchi

doi:10.3762/bjoc.15.199

Abstract

The synthesis of benzimidazo[2,1-b]benzoselenoazoles is described. The novel ring-closure reaction of 1-(2-bromoaryl)benzimidazoles with Se powder is promoted by Cs2CO3 (2 equiv) in DMF at 150 °C. Moreover, the obtained tetracyclic heterocycles are all novel compounds. Single-crystal X-ray analysis of the parent benzimidazo[2,1-b]benzoselenoazole revealed that the tetracyclic ring is almost planar. Absorption spectroscopy data of the benzimidazo[2,1-b]benzoselenoazoles showed the λmax was dependent on the number of rings.

Highlights

Selenium-containing heterocyclic ring systems have attracted attention because of their chemical properties and reactivities, and for their wide biological activities [1,2,3,4]
We present in this paper the synthesis of benzo[d]imidazo[2,1-b]benzoselenoazoles under transition metal-free conditions by the Cs2CO3mediated cyclization of 1-(2-bromoaryl)benzimidazoles with selenium
We initially focused our attention on determining the optimal conditions for the cyclization of a chalcogen with 1-(2bromophenyl)benzimidazole (1a)

Summary

Introduction

Selenium-containing heterocyclic ring systems have attracted attention because of their chemical properties and reactivities, and for their wide biological activities [1,2,3,4]. Three ring closure reactions for the synthesis of imidazo[2,1b]selenoazole have been reported so far (Scheme 1). We present in this paper the synthesis of benzo[d]imidazo[2,1-b]benzoselenoazoles under transition metal-free conditions by the Cs2CO3mediated cyclization of 1-(2-bromoaryl)benzimidazoles with selenium.

Results

Conclusion