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

Abstract

This study reports two synthetic approaches leading to 2-aminobenzoxazoles and their <i>N</i>-substituted analogues. Our first synthetic strategy involves a reaction between various <i>o</i>-aminophenols and <i>N</i>-cyano-<i>N</i>-phenyl-<i>p</i>-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.