Creating skeletal complexity through an interrupted Corey-Chaykovsky reaction of activated alkynes.

We present the first interrupted Corey-Chaykovsky reaction of α,β-ynones by intercepting the zwitterionic intermediates that prevail during the addition of the Corey-Chaykovsky reagent to activated alkynes. This cascade transformation uncovers a novel mechanistic feature and leverages it to construct complex polycyclic molecular architectures featuring three new carbon-carbon bonds, four new carbo- and heterocycles and four contiguous stereocenters, two of which are quaternary carbons, all in a single-pot operation. Additionally, we demonstrate the synthetic utility of these otherwise unprecedented molecules.