Formation of a Stable Rhodium(I) Dihydride Complex and Its Reactions with Prochiral Substrates of Asymmetric Hydrogenation
作者:Ilya D. Gridnev、Natsuka Higashi、Tsuneo Imamoto
DOI:10.1021/om010251w
日期:2001.10.1
secondary phosphine-borane 4 via the corresponding diphosphine-borane 3. The Rh(I) complex (2) of 1 was characterized by X-ray study, which revealed a significantly distorted C2-symmetry. The catalytic hydrogenation of four representative prochiral substrates gave modest enantioselection. Unlike all previously studied Rh(I) complexes of chiral diphosphines, 2 reacts with dihydrogen at −70 °C, producing
通过旋光性仲膦-硼烷4经由相应的二膦酸酯-分两步合成了一种新的P-手性二膦(S,S)-α,α'-双(叔丁基甲基膦基)-邻二甲苯(1)。硼烷3。Rh(I)配合物(2)为1的特征是通过X射线研究确定的,该结果表明C 2对称性明显失真。四个代表性手性底物的催化加氢给出适度的对映体。与以前研究的所有手性二膦Rh(I)配合物不同,2在-70°C下与二氢反应,生成比例为1:0.07的两个溶剂化物二氢化物5a和b的非对映异构体。5a,b的形成几乎是定量的;没有从5中除去氢。在高于20°C的温度下,发生5的进一步转化,最终产生桥联双核络合物6。的反应5用甲基ž - (α)乙酰胺基肉桂(7)是在-80℃下缓慢,和的单氢化物中间体的混合物的逐渐累积部15a - d可以通过监测11 H NMR光谱。当5与1-苯甲酰氧基乙烯膦酸二甲酯(10)反应时,两种单氢化物中间体19a,b以1:0.04的比率干净地形成,对应