Lewis Acid-Catalyzed [4+2] Annulation between Propargylic Alcohols with Benzo[d]isoxazoles

An unprecedented copper(II) trifluoromethanesulfonate-catalyzed [4+2] cascade annulation of propargylic alcohols with benzo[d] isoxazoles proceeds through a sequential ring opening/Meyer-Schuster rearrangement/intermolecular cyclization. This protocol, which tolerates a broad variety of functional groups, offers a versatile, modular and atom-economical access to a new class of fascinating quinoline derivatives in good yields under mild conditions. The transformation could be scaled up to a gram scale efficiently, thus highlighting the synthetic utility of this methodology.