A Low-Temperature Ammonium Ylid Rearrangement: Enhanced Reactivity Engendered by Rigidity

Abstract

L o w -T e m p e r a t u r e A m m o n i u m Y l i d R e a r r a n g e m e n t Abstract: Sigmatropic rearrangement of tetrahydropyridinederived ammonium is a valuable method for the preparation of substituted prolines. These reaction normally require elevated temperatures to proceed, but bicyclic tetrahydropyridine-like ylid 1 undergoes rearrangement at -15 °C; the extra rigidity of the azabicyclo[3.3.0]octene system preorganizes the transition state and lowers the activation energy for rearrangement.