Direct Synthesis of Benzothiazoles and Benzoxazoles from Carboxylic Acids Utilizing (<i>o</i>-CF₃PhO)₃P as a Coupling Reagent

A general and efficient method for the direct synthesis of benzothiazoles and benzoxazoles from carboxylic acids with 2-aminobenzenethiols or 2-aminophenols using (<i>o</i>-CF₃PhO)₃P as a simple coupling reagent has been developed. Diverse benzothiazoles and benzoxazoles were synthesized in moderate to excellent yields. And the gram-scale preparation of benzothiazole and benzoxazole also proceeded smoothly under the mild conditions. Moreover, a plausible reaction mechanism was discussed, with (<i>o</i>-CF₃PhO)₃P and its hydrolysis product (<i>o</i>-CF₃PhO)₂P(O)H contributing to the formation of the target products as an amide synthesis coupling agent and a cyclization reaction promoter, respectively.