One-pot synthesis of 2-aminobenzoxazole derivatives using acetic acid as an electrolyte under electrochemical conditions

TLDR: In this article, an electrochemical method to prepare 2-aminobenzoxazole by using acetic acid as an electrolyte was developed, which was shown to be robust, scalable and having a broad substrate scope.

Abstract: In this work, we have developed an electrochemical method to prepare 2-aminobenzoxazole by using acetic acid as an electrolyte. The key benefits of this method are being cleaner reaction pattern with minimum impurity formation, no metal catalyst used, high atom economy, robust, scalable and having a broad substrate scope. Previously, electrochemical conversions were reported with the addition of a supporting electrolyte such as tetrabutyl ammoniumbromide, sodium iodide and lithium perchlorate, but in this conversion we have removed the use of all supporting electrolytes and we have used acetic acid, which plays a dual role of opening the benzoxazole moiety and works as an electrolyte. All these electrochemical conversions were done on a electrochemical reactor prepared through a 5v mobile charger having a output current density of 0.35A.cm−2. Various pharmaceutically relevant secondary amines are coupled with benzoxazole in high yield by using this set-up. All the conversions were done at room temperature and total conversion observed in 6 h. The scale of the conversion ranges from milligram to gram. Active intermediate of Suvorexant, a medicine for insomnia, was prepared by using this method.