Synthesis of chiral 1-ferrocenylaldols and 1-ferrocenyl-1,3-diols via asymmetric reductions

The asymmetric transfer hydrogenation promoted by the (R,R)-(Ts-DPEN)-Ru complex of some 1-ferrocenyl-1,3-diketones was investigated and in all the cases only the carbonyl group distant to the metallocene moiety was reduced with variable selectivity depending on the C-3 substituent. The CBS-catalyzed reduction of 1-ferrocenyl-beta-hydroxy-1-ketones, previously protected as acetates, was also found effective, giving both the corresponding syn- and anti-1,3-diols in satisfactory enantiomeric purity.