Reductive Desymmetrization of 2-Alkyl-1,3-diketones Catalyzed by Optically Active β-Ketoiminato Cobalt Complexes

[reaction: see text] The reductive desymmetrization of acyclic 1,3-diketones was achieved for the first time by catalytic borohydride reduction in the presence of optically active beta-ketoiminato cobalt(II) complex catalysts. In this reaction, various 2-substituted-1,3-diaryl-1,3-propanediones were converted into the corresponding optically active 2-substituted-1,3-diaryl-3-hydroxypropanone in good-to-high yields with excellent diastereo- and enantioselectivities and high catalytic efficiencies.