CHIRAL BENZOQUINONES AS A NEW CLASS OF LIGANDS FOR ASYMMETRIC CATALYSIS - SYNTHESIS AND APPLICATION TO THE PALLADIUM(II)-CATALYZED 1,4-DIALKOXYLATION OF 1,3-DIENES

Chiral C-2-symmetric 2,5-bisamide hydroquinone ligands, with beta-amin o alcohols as chiral building units, were synthesized in excellent ove rall yields. The ligands gave up to 54.4% ee in the palladium-catalyze d 1,4-dialkoxylation of 1,3-dienes. These findings demonstrate the pot ential of asymmetric induction utilizing chiral benzoquinones as ligan ds in palladium(II) catalysis, albeit with modest enantiomeric excesse s. Weakly coordinating hydroxyl groups of the ligand appear to be cruc ial for the success of the reaction. Mechanistic aspects and the origi n of enantioselectivity are also discussed.