Synthesis of Dibenzophospholes by Tf₂O‑Mediated Intramolecular Phospha-Friedel–Crafts-Type Reaction

A Tf₂O-mediated intramolecular phospha-Friedel–Crafts-type reaction of secondary biarylphosphine oxides has been developed. The reaction is promoted simply by Tf₂O to form the corresponding dibenzophospholes under metal-free conditions. The starting substrates are readily available and easy-to-handle phosphine oxides, and the regioselectivity is controlled by the innate electronic nature. Thus, this newly developed protocol can provide concise and complementary approach to the highly π-conjugated dibenzophospholes of potent interest in material chemistry.