Lewis Acid Mediated Asymmetric [2,3]-Sigmatropic Rearrangement of Allylic Amines. Scope and Mechanistic Investigation

The first asymmetric [2,3]-sigmatropic rearrangement of achiral allylic amines has been realized by
quaternization of the amines with an enantiomerically pure diazaborolidine and subsequent treatment
with Et3N. The resultant homoallylic amines were obtained in good yields and excellent ee's. The observed
diastereo- and enantioselectivities were rationalized by invoking a kinetically controlled process, and
support for this model was obtained from an NMR spectroscopic investigation of the chiral Lewis acid−substrate complex. The structure of the Lewis acid−product complex was established by X-ray
crystallographic analysis and supported the proposed mechanism.