RHODIUM(I)-CATALYZED, IRIDIUM(I)-CATALYZED, AND RUTHENIUM(II)-CATALYZED ASYMMETRIC TRANSFER HYDROGENATION OF KETONES USING DIFERROCENYL DICHALCOGENIDES AS CHIRAL LIGANDS

R,S;R,S]-Bis[2-[1-(dimethylamino)ethyl]ferrocenyl] dichalcogenides, (R ,S)-{[EC5H3CHMe(NMe2)]Fe(C5H5)}(2) (E = S, Se, Te), act as chiral liga nds for Rh(I)-catalyzed asymmetric transfer hydrogenation of alkyl ary l ketones using a diphenylsilane/methanol system to give the correspon ding alcohols in fair to good yields with moderate enantiomeric excess (22-95% ee). The transfer of hydrogen from methanol to the resultant alcohol is confirmed by experiment using deuterated methanol (MeOD), a nd a new catalytic system containing Rh-hydride species is proposed. I n the well-known 2-propanol/base system, the stereoselection is not sa tisfactory for Rh(I)-, Lr(I)- and Ru(II)-catalyzed reactions using the se ligands.