Direct Synthesis of Benzothiazoles and Benzoxazoles\nfrom Carboxylic Acids Utilizing (<i>o</i>‑CF<sub>3</sub>PhO)<sub>3</sub>P as a Coupling Reagent

A general and efficient method for the direct synthesis\nof benzothiazoles\nand benzoxazoles from carboxylic acids with 2-aminobenzenethiols or\n2-aminophenols using (<i>o</i>-CF<sub>3</sub>PhO)<sub>3</sub>P as a simple coupling reagent has been developed. Diverse benzothiazoles\nand benzoxazoles were synthesized in moderate to excellent yields.\nAnd the gram-scale preparation of benzothiazole and benzoxazole also\nproceeded smoothly under the mild conditions. Moreover, a plausible\nreaction mechanism was discussed, with (<i>o</i>-CF<sub>3</sub>PhO)<sub>3</sub>P and its hydrolysis product (<i>o</i>-CF<sub>3</sub>PhO)<sub>2</sub>P(O)H contributing to the formation\nof the target products as an amide synthesis coupling agent and a\ncyclization reaction promoter, respectively.