Diastereoselective Synthesis of Diquinanes and Triquinanes Bearing Vicinal Quaternary Carbon Stereocenters from Acyclic Allene-based Precursors via a Cascade Reaction.

A cascade benzenethiol-mediated intramolecular [3 + 2] cycloaddition reaction between an allene and an α,β-unsaturated aldehyde or ester is developed for the diastereoselective synthesis of [3.3.0] bicyclic system bearing two quaternary atoms at their bridgehead positions. Notably, these structurally complex systems can be found in a wide range of natural products.