Enantioselective catalytic conjugate addition of dialkylzinc reagents using copper-phosphoramidite complexes; Ligand variation and non-linear effects

A variety of new chiral phosphoramidites was synthesised and tested in the copper-catalysed enantioselective conjugate addition of diethylzinc to cycl ohexenone and chalcone in order to assess the structural features that are important for stereocontrol. A sterically demanding amine moiety is essenti al to reach high e.e.'s. Enantioselectivities for chalcones up to 89% and f or cyclic enones up to 98% were found. Studies on non-linear effects with t he best ligands for both cyclohexenone and chalcone showed clear non-linear effects for both cyclic and acyclic enones. (C) 2000 Elsevier Science Ltd. All rights reserved.