Tandem 1,6-Addition/Annulations of Alkynyl p -Quinone Methides with Bis-nucleophiles: Entry to Functionalized Furans, Isoxazoles, Pyrazoles, and Pyridines.

The reaction of alkynyl p -quinone methide ( p QM) with keto-methylenes through a base-mediated tandem 1,6-addition/annulation sequence, [2 + 3] annulation, affording the furans is reported for the first time. A variety of functionalized furans, including fused derivatives, were obtained in good to excellent yields under mild reaction conditions. The efficacy of alkynyl p QMs is highlighted by extending their use to access isoxazoles, pyrazoles via [3 + 2] annulation, and pyridines through [3 + 3] annulation in the presence of different bis-nucleophiles.