Palladium(II) and BF3·OEt2 Cooperatively Catalyzed Regioselective Cyclization of Alkynyl-Tethered Aryl Ethers with Hydrogen-Bonding Interactions

Herein, we report palladium(II) and BF₃·OEt₂ cooperatively catalyzed regioselective ipso-cyclization of alkynyl-tethered para-methoxylated arenes and ortho-cyclization of alkynyl-tethered arenes to prepare spiropyrrolo[2,1-b]quinazolinone-cyclohexadienones and 2,3-fused quinazolinones in good to excellent yields with high regioselectivity, respectively. DFT calculations revealed that the self-assembly of hydrogen-bonding between OAc anion and hydrogen atom of terminal alkyne facilitated ipso-cyclization for the para-methoxy group on the N-aryl moieties. The present method features broad substrate scope, palladacycle as the real catalyst, and hydrogen-bonding enhanced regioselective hydroarylation cyclization.