Selenopheno[2,3-e][1,2,4]triazolo[4,3-c]pyrimidine: A novel tricyclic selenium containing heterocyclic system

Selenium (Se) is an essential trace element for human, for example, many kinds of selenoproteins have an important role in human metabolism [1]. The interest in thesynthesis of selenium-containing compounds has increased remarkably due to the discovery of various derivatives with potential biological and pharmaceutical activities. For instance, the practical application of such compounds in medicine for the treatment of tumors and cancers is a subject of current intense interest [2]. On the other hand, the synthesis of fused selenophenes has begun to play an important role in the design and synthesis of conducting, superconducting and magnetic materials [3].Initially, concentrated sulfuric acid mediated hydrolysis of compound (1) gave the corresponding selenophene-2-carboxamide (2) which subsequently underwent thecyclization reaction with triethylorthoformate to give selenopheno[3,2-d]pyrimidine (3). In continuation, compound (3) treated with POCl3 and NH2NH2 to give the chlorinated and hydrazinated compounds (4) and (5), respectively. The heterocyclization reaction of the latter compound with a few triethylorthoesters yielded quantitatively the desired tricyclic selenopheno[2,3-e][1,2,4]triazolo[4,3- c]pyrimidines (6a-c).