Stereocontrolled α-Allylation of α-Branched --Butanesulfinyl Ketimines via a Michael-Wittig Cascade for the Construction of Acyclic Quaternary Stereocenters.

A single-flask cascade of Michael addition and Wittig olefination was developed to allow the stereoselective α-allylic alkylation of α-branched --butanesulfinyl ketimines for the construction of acyclic quaternary stereocenters bearing two sterically and electronically similar substituents. In this process, BuOK-promoted stereoselective α-deprotonation gives fully substituted aza-enolates with a stereodefined geometry, Michael addition with α,β-unsaturated phosphonates generates C-C bonds with exceptional stereocontrol, and finally paraformaldehyde trapping of the conjugate addition intermediate generates functionalized α-allylated imines.