Phosphine-oxazoline ligands with an axial-unfixed biphenyl backbone: the effects of the substituent at oxazoline ring and P phenyl ring on Pd-catalyzed asymmetric allylic alkylation
作者:Fengtao Tian、Dongmei Yao、Yong Jian Zhang、Wanbin Zhang
DOI:10.1016/j.tet.2009.09.053
日期:2009.11
These compounds as chiral ligands were applied in Pd-catalyzed asymmetric allylic alkylation with high reaction activity and enantioselectivity. Meanwhile, the asymmetric catalytic behavior was affected obviously by the substituent at oxazoline ring and P phenyl ring. The best result, up to 92.3% ee and 99% yield, was obtained with the ligand 3c having two phenyl groups on P and a phenyl group on oxazoline
制备了一种新型的手性膦-恶唑啉配体3,其轴向未固定的联苯骨架在恶唑啉环和P苯基环上带有不同的取代基。这些配体以两种非对映异构体的混合物形式存在于溶液中,处于平衡状态。然而,当与Pd(II)配位时,仅形成了两种可能的具有不同轴向手性的非对映异构体复合物中的一种。这些化合物作为手性配体被应用于钯催化的不对称烯丙基烷基化反应中,具有很高的反应活性和对映选择性。同时,恶唑啉环和P苯环上的取代基对不对称催化行为有明显的影响。使用配体3c可获得最佳结果,ee高达92.3%,产率高达99% 在该不对称催化反应中,在P上具有两个苯基并且在恶唑啉环上具有苯基。