Practical (asymmetric) transfer hydrogenation of ketones catalyzed by manganese with (chiral) diamines ligands

The reduction of ketones with 2-propanol as reductant was achieved using an in-situ generated catalytic system based on manganese pentacarbonyl bromide, as metal precursor, and ethylenediamine as ligand. The reaction proceeds in high yield at 80 degrees C, in 3 h, with 0.5 mol% of catalyst. In the presence of chiral (1R,2R)-N,N'-dimethyl-1,2-diphenylethane-1,2-diamine, as the ligand, sterically hindered alcohols were produced with enantiomeric excess up to 90%.