Microwave-Enhanced On-Water Amination of 2-Mercaptobenzoxazoles To Prepare 2-Aminobenzoxazoles

In this work, we developed a catalyst-free amination of 2-mercaptobenzoxazoles on water under microwave irradiation. The product, 2-aminobenzoxazoles, was successfully produced via direct amination with various amines in moderate to high yields. The formal synthesis of Suvorexant, a medication for the treatment of insomnia, was accomplished using a developed amination process. The reaction was completed in an hour at 100-150 °C in a microwave reactor without the use of external catalyst or additive. Key benefits of this process include an on-water reaction, short reaction time, being scalable and catalyst-free, and use of 2-mercaptobenzoxazoles as an inexpensive starting material having low environmental impact in its preparation.