Steering reaction pathways: From benzyl Claisen rearrangements to powerful ionic shifts

Abstract

Take a walk on the wild side: A novel benzyl Claisen cascade rearrangement of keteniminium salts is described. The reaction leads to α-arylated lactones under metal-free conditions (top scheme; Tf=trifluoromethanesulfonyl). It is further demonstrated that the cationic intermediates involved can be steered away from pericyclic reaction manifolds into powerful ionic shifts through reaction design (bottom scheme). Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.