Ikariya Takao, Gridnev Ilya D
Department of Applied Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Japan.
Chem Rec. 2009;9(2):106-23. doi: 10.1002/tcr.20172.
This paper describes the recent advances in the conceptually new bifunctional Ir and Ru catalysts for asymmetric catalytic reactions. These reactions include the enantioselective Michael addition of 1,3-dicarbonyl compounds to cyclic enones and nitroalkenes, and the enantioselective direct amination of alpha-cyanoacetates with diazoesters. The outcome of these reactions in terms of reactivity and selectivity was delicately influenced by the catalyst structures and the reaction conditions including the solvents used. Even with a 1 : 1 molar ratio of donors to acceptors, the reactions proceeded smoothly to give the corresponding chiral adducts with an excellent yield and enantiomeric excess (ee). Preliminary mechanistic studies showed that the key stage of the catalytic cycle is the interaction of the bifunctional catalyst with a pronucleophilic reagent that leads to stereoselective formation of C-, O-, or N-bound complexes. The resulting protonated catalyst bearing metal-bound nucleophiles readily reacts with electrophiles to provide C--C and C--N bond formation products in a highly stereoselective manner.
本文描述了用于不对称催化反应的概念全新的双功能铱和钌催化剂的最新进展。这些反应包括1,3 - 二羰基化合物对环状烯酮和硝基烯烃的对映选择性迈克尔加成反应，以及α - 氰基乙酸酯与重氮酯的对映选择性直接胺化反应。这些反应的反应性和选择性结果受到催化剂结构以及包括所用溶剂在内的反应条件的微妙影响。即使供体与受体的摩尔比为1:1，反应也能顺利进行，以优异的产率和对映体过量（ee）得到相应的手性加合物。初步机理研究表明，催化循环的关键阶段是双功能催化剂与亲核前体试剂的相互作用，这导致立体选择性地形成碳、氧或氮键合的配合物。生成的带有金属键合亲核试剂的质子化催化剂很容易与亲电试剂反应，以高度立体选择性的方式提供碳 - 碳和碳 - 氮键形成产物。
