Borohydride reduction of acetophenone and esters of dehydrocarboxylic acids in the presence of chiral cobalt(II) diamine complexes

The catalytic reduction of acetophenone, methyl alpha-acetamidocinnamate, and dimethyl itaconate with alcohol - modified sodium borohydride was studied in the presence of complexes (CoCl2L2)-L-. (L-2 are chiral C-2-symmetric diamines: (4S,5S)-2,2-dimethyl-4,5-bis(aminomethyl)-1,3-dioxolane, (4S,5S)-2,2-dimethyl-4,5-bis(methylaminomethyl)-1,3-dioxolane, (4S,5S)-2,2-dimethyl-4,5-bis(dimethylaminomethyl)-1,3-dioxolane, and (4S,5S)-2,2-dimethyl-4,5-bis(diphenylaminomethyl)-1,3-dioxolane). The maximum enantiomeric excess of (S)-1-phenylethanol was 24%, that of dimethyl alpha-methylsuccinate was 38 %.