Isotopic Desymmetrization in the Study of Homogeneous Catalysis.

NMR studies on isotopically desymmetrized ligands and substrates have been used to demonstrate and investigate an apparent "memory effect" in palladium-catalysed nucleophilic substitution at allylic centres. The explanation for this "memory effect" is shown to be the participation of both monomeric and oligomeric complexes, with different reaction rates. [ABSTRACT FROM AUTHOR]