Cu(I)-Catalyzed Tetradehydro-Diels–Alder Reaction of Enediynols: Modular Assembly of Multi-substituted Fluorenols

An efficient and regioselective intramolecular tetradehydro-Diels-Alder (TDDA) reaction of enediynols has been realized under mild conditions. This strategy provided a general, concise, and atom-economical approach to synthesize a diverse array of functionalized fluorenols. In addition, the corresponding fluorenol products are readily converted to highly substituted phenanthrene and benzo[<i>b</i>]fluorene derivatives. Control experiments revealed that the newly developed CuI/<i>ortho</i>-phenylenediamine catalytic system greatly enhanced the reactivity of this transformation.