CHIRAL ARENE RUTHENIUM COMPLEXES .2. A DIASTEREOSELECTIVE ROUTE TO [(ETA(6)-BENZYL ALCOHOL)(COD)RU] COMPLEXES

Two preparative routes are reported that give access to the racemic se ries of planar chiral [(arene)(COD)Ru] derivatives containing eta(6)-b onded o-tolyl ketone or aldehyde arene units. The ketone and aldehyde functions of these have subsequently been reduced by nBuLi and PhLi, r espectively. Hydrolysis converts the initially formed lithium salts in to diastereomeric benzyl alcohol complexes in high yields. The formati on of the new stereogenic centre is diastereoselective (88% de) for th e aldehyde and diastereospecific for the ketone (de > 99%). Due to a s terically overcrowded situation, the rotation of the chiral side chain of [(COD)(eta(6)-o-tolyl-tert-butylphenylmethanol) Ru] (7) is hindere d, as is the rotation of the phenyl and tert-butyl substituents. As a consequence, the hydroxyl group is fixed at a position close to the me tal both in solution and in the solid state.