Synthesis of Various 2-Aminobenzoxazoles: The Study of Cyclization and Smiles Rearrangement.

This study reports two synthetic approaches leading to 2-aminobenzoxazoles and their -substituted analogues. Our first synthetic strategy involves a reaction between various -aminophenols and -cyano--phenyl--toluenesulfonamide as a nonhazardous electrophilic cyanating agent in the presence of Lewis acid. The second synthetic approach uses the Smiles rearrangement upon activation of benzoxazole-2-thiol with chloroacetyl chloride. Both developed synthetic protocols are widely applicable, afford the desired aminobenzoxazoles in good to excellent yields, and use nontoxic and inexpensive starting material.