Unusual participation of -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[,]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. An unusual participation of the O -propargyl alkyne group during the cyclization of 6-hydroxy-2-propargyl ethers of aryl chalcones afforded highly functionalized 2-acyl-3-styrylbenzofuran and 8-aryl dibenzo[ b , d ]furan-1,7-diol derivatives. A plausible mechanism and scope of the reaction is provided.