Enantioselectivity in the catalytic hydroesterification of acenaphthylene: direct evidence of the racemization of PdIIalkyl species by a degenerate substitution equilibrium with Pd0Ln

The palladium catalyzed hydroesterification of acenaphthylene takes place through a "hydride" mechanism, that is, through the selective cis insertion of the olefin into the palladium–hydride bond, an obvious prerequisite for the successful development of an enantioselective version of the reaction; however, a degenerate substitution equilibrium between Pd0Ln and the PdII-alkyl species, involving the inversion of the alkyl carbon, is also operative producing a detrimental effect in the enantioselectivity of the reaction.