Iodine-Promoted Tandem Annulation/Aromatization: A Route to Substituted Dibenzofurans

An efficient and practical method for the preparation of polysubstituted dibenzofurans has been developed via the iodine-catalyzed tandem cyclization of readily available aurones with 2-(2H-benzo[b][1,4]thiazin-3(4H)-ylidene)acetate ester derivatives. This one-pot cascade reaction involves Michael addition, intramolecular cyclization, and aromatization, affording a wide range of functional dibenzofuran derivatives in moderate to good yields. Notably, this unprecedented protocol offers several advantages, including metal-free conditions, a broad substrate scope, an inexpensive and nontoxic catalyst, high atom economy, applicability for gram-scale synthesis, and access to structurally novel dibenzofuran frameworks.