Selenium used to be considered as an essential nutrient, constituent of selenoproteins involved in self-defense mechanism against oxidative stress,1 in reducing certain inflammatory processes and in detoxification processes 2. Based on the benefits associated to the presence of selenium, the synthesis of many heterocyclic systems characterized by a large variety of biological activities was developed. Among them, amino-1,3-selenazole ring systems have received much attention from medicinal chemists worldwide because of their wide range of biological activity, such as antimicrobial, anti-HIV, antioxidant and anticancer, among others.3,4 Due to widespread biological activities of 1,3-selenazols and our interest for the synthesis of selenazolocondenced heterocyclic systems, in the present protocol, concentrated sulfuric acid mediated hydrolysis of compounds 1 (a-c) gave the corresponding 4-amino-1,3-selenazole-5-carboxamides 2 (a-c) which subsequently underwent the heterocyclization reaction with some triethylorthoesters to yield various derivatives of a novel heterocyclic system of [1,3]selenazolo[4,5-d]pyrimidine 3 (a-i) in excellent yields with potential biological activities.

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