Evidence for a non-concerted, dissoziative mechanism of the palladium-catalyzed 'enolate Claisen rearrangement' of allylic esters

摘要

In an enolate Claisen rearrangement, deprotonated allyl phenylacetate undergoes a smooth conversion at -78 °C to 2-phenyl-4-pentenoic acid under palladium(O) catalysis. By using labelled starting materials in crossover experiments, the reaction is shown to follow a dissoziative, non-concerted, non-[3,3]-sigmatropic mechanism that involves palladium complexes and carboxylic-acid dianions as intermediates.