Unsymmetrical terdentate phosphorus-nitrogen-nitrogen (PNN) ligands: Effect of the M/L ratio and the pendant group on stereoselectivity

Abstract

Twelve novel, unsymmetrical terdentate pyrrolidine-based phosphorus-nitrogen ligands were prepared. These ligands promoted very high catalytic activity in the palladium-catalysed allylic substitution reactions of 1,3-diphenylpropenyl acetate with malonate esters (100% conversion at 0°C in <2 h). Enantioselectivities up to 94% were attained. An unusual effect of metal-to-ligand ratio was observed. Various structural features affecting the enantioselectivity and stereoinduction were examined and discussed. © 2003 Elsevier Ltd. All rights reserved.