SYNTHESIS OF NOVEL CHIRAL OLIGOPYRIDINE DERIVATIVE LIGANDS FOR THE ENANTIOSELECTIVE ADDITION OF DIETHYLZINC TO BENZALDEHYDE

Several chiral dipyridine and dithiophene derived ligands have been pr epared from readily available homochiral materials such as ethyl L-lac tate and naproxene methyl ester, based on the dialkylation strategy us ing heterocyclic organometallic reagents. Each of these chiral ligands was used for the catalytic enantioselective addition of diethylzinc t o benzaldehyde. The best result was obtained for 3: 70% ee was achieve d. A plausible mechanism for this asymmetric induction is offered, bas ed on X-ray crystallographic data. (C) 1998 Elsevier Science Ltd. All rights reserved.