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 NaHCO 3 to provide the desired quinone products in good to excellent yields.