Construction of P-Chiral Reaction Field by Y-P-Y type Chiral Ligands and Application to Multi-site Controlled Asymmetric Reactions

具有两个配位单元的对称Y-P-Y配体，当其中一个y -单元与金属发生选择性连接时，有望形成p -手性中心，并在不对称反应的反应位点附近构建有效的手性场。残留的Y基与底物或反应试剂相互作用，实现多位点识别，产生更高的手性诱导。作为N-P-N型配体，制备了具有两个手性恶唑啉单元((S，S)-R-P（x-R′）_2)（R=Ph, ^iPr; R′=Me, ^iPr, ^tBu）的多种双恶唑啉配体，并通过核磁共振技术研究了它们与Pd、Pt、Rh、Ni、Ru的配位模式。在方形平面配合物中，通过选择性地将两个恶唑啉单元中的一个连接到金属上，观察到与非对映异构体配合物中的一个平衡有很大的偏差。通过对[Pd(C_3H_5)-((S，S)- php (x-i^Pr)_2]PF_6单晶的x射线分析，也证实了这种选择性连接提供p -手性中心的作用。将双恶唑膦Pd配合物应用于不对称烯丙基烷基化和活化；在对映异构分化烯丙基烷基化反应中，获得了90%以上的高对映选择性，特别是在具有小空间因子的1,3-二甲基-π-烯丙基中间体的亲核反应中，获得了94%的ee，这是迄今为止报道的最高值。这些结果表明选择性结扎形成的p -手性中心是有效的。在钯催化下，烷基锌化合物与π-烯丙基中间体的反应中，观察到游离恶唑基对多位点控制反应的贡献。

Symmetrical Y-P-Y ligands having two coordinating units would be expected to form a P-chiral center if selective ligation of one of Y-units to metals occurs and to construct an effective chiral filed near the reaction site for asymmetric reactions. Residual Y unit would serve to interact with substrate or reaction reagent to realize the multi-site recognition to cause higher chiral induction. As N-P-N type ligand, various chiral bisoxazolylphosphine ligands having two chiral oxazoline units ((S,S)-R-P(Ox-R')_2) (R=Ph, ^iPr ; R'=Me, ^iPr, ^tBu) were prepared and their coordination mode to Pd, Pt, Rh, Ni, or Ru were examined by NMR technique. In the square planar complexes, large deviation in equilibrium to one of diastereomeric complexes was observed by the selective ligation of one of two oxazoline units to metal. This selective ligation to afford P-chiral center was also clarified by the X-ray analysis of a single crystal of [Pd(C_3H_5)-((S,S)-PhP(Ox-i^Pr)_2]PF_6.Bisoxazolylphosphine Pd complexes were applied to the asymmetric allylic alkylation and animation; In the enantiotopos differentiating allylic alkylation, high enantioselectivity more than 90 %ee were obtained, especially in the nucleophilic reaction of 1,3-dimethyl-π-allyl intermediate with a small steric factor 94% ee was obtained, which is the highest value reported so far. These results indicate the effectiveness of the P-chiral center formed by the selective ligation. In the reaction of alkyl zinc compound with π-allyl intermediate by Pd catalyst, the contribution of the free oxazolyl unit was observed to cause multi-site controlled reaction.