Synergistic Lewis–Brønsted Acid Catalysis in Cascade Cyclization of ortho-Alkynylaryl Cyclopropylketones for the Synthesis of 2,3-Dihydronaphtho[1,2‑b]furans

In this work, a synthetic method for the synthesis of 2,3-dihydro­naphtho­[1,2-b]­furans employing synergistic Lewis–Brønsted Acid catalyzed cyclization of ortho-alkynyl­arylcyclo­propylketones has been developed. Benefits of our method included low catalyst loading, low cost of catalyst, short reaction time, and mild conditions which could be applied to a broad range of substrates, including a terminal alkyne (R = H), to provide generally high yields of the desired products. In addition, we found that 2,3-dihydronaphtho­[1,2-b]­furan derivatives could be isomerized to give 5,6-dihydrotetraphen-7-ol anaologs under acidic conditions via Friedel–Crafts-type alkylation in good to excellent yields. However, these products were not stable and gradually converted to the corresponding quinones. The competent transformation was successfully obtained by treating with m-CPBA in the presence of NaHCO3 to provide the desired quinone products in good to excellent yields.