取代基对手性唑噁唑硼烷催化还原苯基乙基酮对映体选择性影响的理论研究

用AM1方法和过渡态理论研究了取代基对含侧链手性噁唑硼烷催化还原苯 基乙杂程逖≡裥缘挠跋欤扑憬峁砻鳎杂逞≡裥匀【鲇?R)和(S)两个对映体? 叫蟹从Φ乃俾食Ｊ龋盋(4)和C(5)位上的取代基呈顺式时，所得对映体以(R) 型为主．对映选择性的高低与噁唑硼烷环上不同位置原子连接的取代基基团的大? ∮泄兀扑憬峁胧笛樽芙岢龅慕崧巯辔呛希? $601 $AThe influence of substituents on the enantioselectivity in asymmetric branched-oxazaborolidine-catalyzed reductions of phenyl- ethyl ketone has been studied by using AMI MO method and transition state theory. The results show that the enantioselectivity is determined by the ratio of the rate constants of two parallel reactions conducting to spatial configurations (R) and (S). When the substituents connecting with C(4) and C(5) are in cis-form the reduction products of phenyl-ethyl ketone in the reactions are mainly of configuration ( R). In asymmetric boron-catalyzed reduction reactions the higher or lower magnitude for enantioselectivity and reaction barrier are governed by various substituents connecting with atoms of oxazaborolidine ring. The computational results are in consistence with experiments.

Theoretical Study on the Influence of Substituents on Enantioselecthity in Branched-Oxazaborolidine-Catalyzed Reductions of Phenyl-ethyl Ketone

The influence of substituents on the enantioselectivity in asymmetric branched oxazaborolidine catalyzed reductions of phenyl ethyl ketone has been studied by using AM1 MO method and transition state theory. The results show that the enantioselectivity is determined by the ratio of the rate constants of two parallel reactions conducting to spatial configurations (R) and (S) . When the substituents connecting with C(4) and C(5) are in cis form the reduction products of phenyl ethyl ketone in the reactions are mainly of configuration (R) . In asymmetric boron catalyzed reduction reactions the higher or lower magnitude for enantioselectivity and reaction barrier are governed by various substituents connecting with atoms of oxazaborolidine ring. The computational results are in consistence with experiments.