Transition-State Complexation in Palladium-Promoted [3,3] Sigmatropic Shifts

摘要

The mechanism of the Cope rearrangement (the [3,3]-sigmatropic shift of a 1,5-nexadiene) has long stood as a point of debate. Much of the controversy was a result of its "chameleonic" behavior; namely, its mechanism varies between concerted and stepwise pathways depending on the nature and position of appended substituents. Nonetheless, this reaction has been used as a key step in many creative and elegant syntheses.