Unusual participation of O-propargyl group during the cyclization of 6-hydroxy-2-propargyl ethers of aryl chalcones: one-pot synthesis of 2-acyl-3-styrylbenzofuran and 7-aryldibenzo[b,d]furan-1,7-diols

The mercuric acetate-pyridine-mediated cyclization reaction of aryl O-propargyl ethers of chalcones provided 8-phenyl-dibenzo[b,d]furan-1,7-diol and (E)-1-(4-hydroxy-3-styrylbenzofuran-2-yl)ethan-1-one via an unusual participation of O-propargyl group of ortho propargyl ethers is observed. The scope and limitations of the reaction and synthetic use of the products are provided. Based on control experiments and isolated products, a plausible reaction mechanism for forming unusual title compounds is provided.