Lewis Acid Mediated [2,3]-Sigmatropic Rearrangement of Allylic Ammonium Ylides

Abstract: This thesis describes a Lewis acid mediated[2,3]-sigmatropic rearrangement of various allylic ammoniumylides. Several Lewis acids are investigated and BBr3 and BF3are established to be the Lewis acids providing the highestconversion of the starting allylic amines. The observeddiastereoselectivities for (E)-crotyl and (E)-cinnamyl amineare excellent and a transition state model is proposed toaccount for the observed selectivities. The structures of theintermediate Lewis acid-allylic amine complexes are confirmedby NMR spectroscopy studies and a plausible transition state ispresented based on DFT calculations.As anextension of this investigation, preliminary resultsfrom an asymmetric [2,3]-sigmatropic rearrangement of allylicammonium ylides employing a chiral cyclic bromoborane arepresented.