Synthesis of Furo[2,3‐f]dibenzotropones via Intramolecular Wittig Reaction of Alkylidene Dibenzo‐β‐tropolones

Abstract A strategy was developed for synthesizing furan‐fused dibenzotropones via intramolecular Wittig reactions of alkylidene dibenzo‐ β ‐tropolones and acylating reactants in catalytic or stoichiometric conditions. With these protocols, a series of furo[2,3‐ f ]dibenzotropones were obtained in 49–99% yields within 1–10 hours. Mechanistic studies of the base‐free phenomena revealed that the organophosphane acts both as a mediator and a regenerable Brønsted base under heating.