STUDIES OF ALLYLIC SUBSTITUTION CATALYZED BY A PALLADIUM COMPLEX OF AC-2-SYMMETRICAL BIS(AZIRIDINE) - PREPARATION AND NMR SPECTROSCOPIC INVESTIGATION OF A CHIRAL PI-ALLYL SPECIES

The chiral palladium pi-allyl intermediate for the catalytic asymmetri c synthesis shown in Scheme 1 has been isolated as the PF6- salt. MM2 calculations have been performed and the structure of the palladium co mplex in solution has also been investigated by means of NMR spectrosc opy. Both the computational and spectroscopic results suggest that in the complex the bidentate bis(aziridine) ligand adopts a conformation that forces the pi-allyl moiety out of the normally preferred square-p lanar geometry. This nicely explains the very high enantioselectivity observed in the title reaction.