Sulfinyl-Imine-Assisted Asymmetric [3,3]-Sigmatropic Rearrangement: Generation of Tertiary and Quaternary Stereocenters

An asymmetric chemoselective allylation followed by an oxy-Cope rearrangement sequence is developed to efficiently synthesize chiral β-allylated ketoimines bearing quaternary stereocenters in excellent yields and diastereoselectivities. Besides acting as a nucleophile, allylboronic acid also plays the vital role of a Lewis acid promoter, eliminating the need for adding any external catalyst. Applicability of this method was demonstrated by the total syntheses of flustramine alkaloids.