Triflic Anhydride-Mediated Synthesis of Anthraquinones and Anthrones via Unusual Intramolecular Rearrangement.

Triflic anhydride (TfO) is a potent electrophilic activator for carbonyl groups, facilitating the formation of versatile triflate intermediates that undergo nucleophilic trapping to generate a broad array of valuable compounds. In this work, we have developed a novel method that utilizes TfO as a mediator for carbonyl activation and subsequent intramolecular rearrangement of 3,3-diarylbenzofuranones into anthraquinones 2 and anthrones 3. Both anthraquinones and anthrones are important molecules in the fields of natural products research, pharmaceuticals, and traditional Chinese medicines. A plausible reaction mechanism is proposed involving TfO-mediated activation, carbocation formation, nucleophilic addition, and intramolecular cyclization, ultimately leading to the formation of anthraquinones and anthrones. The developed methodology is both operationally simple and convenient, without the need for an inert atmosphere. This study broadens the scope of TfO utility and extends the practical application of intriguing intramolecular rearrangement to the synthesis of biologically active compounds, pharmaceuticals, and functional materials.