Construction of\nNaphtho[2,1‑<i>d</i>]oxazoles and 1,4-Epoxyisoquinolines\nvia Regioselectivity-Switchable\nDiels–Alder Reaction of 4‑Alkenyloxazoles with Arynes

A Regioselectivity-switchable Diels–Alder reaction\nof arynes\nand 4-alkenyloxazoles was explored. By regulating the reaction temperature\nand the polarity of the solvent, the reaction activity of aryne was\ncontrolled to selectively react with different favorable reaction\nsites of 4-alkenyloxazoles, providing naphtho[2,1-<i>d</i>]oxazoles and 1,4-epoxyisoquinolines. Density functional theory (DFT)\ncalculations demonstrated that the Diels–Alder reaction on\nacyclic dienes site needs more energy than the reaction on cyclic\ndienes to overcome the potential reaction barrier.