In the research and development of pharmacuticals, agricultural chemicals or functional materials starting with ferroelectrical liquid crystals, the demand for optically active compounds has increased more than ever. In order to obtain the desired optically active compounds through synthesis, diastereo-differentiating and enantio- differentiating reactions have employed chiral auxiliaries or asymmetric catalysts. In order to achieve even higher optical purity and yield, new chiral auxiliaries and asymmetric catalysts are being developed and a considerable number of successful results have been reported. For instance, camphorsultam and oxazolidinone derivatives are utilized as chiral auxiliaries. BINAP-Ru complexes and oxazaborolidine derivatives are excellent asymmetric catalysts. All of these new developments produce products of high optical purity and good reaction yields.
Recently, Yamada and co-workers have developed a pro-chiral ketone and imine asymmetric reduction which uses the newly developed optically active cobalt(II) complex catalyst MPAC. Through this asymmetric reduction using MPAC, secondary alcohols and amines of high optical purity can be obtained in good yields. The reaction proceeds under relatively moderate temperatures and utilize sodium borohydride, which has been traditionally employed as a reducing agent of ketones and imines. For this reason, this method is receiving much attention as a route to useful optically active alcohols and amines.
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