面手性和中心手性的二茂铁基六元氮杂环卡宾配体的合成及应用研究

Chiral ferrocene ligands constitute an important class of ligands for transition-metal catalysis due to their unique steric effect, electronic effect, and the easily modified planar and central chiral elements. 6-Membered N-heterocyclic carbene(6-NHC) metal complexes have unique electronic and steric properties.The combination of the 6-NHCs with chiral ferrocene moiety will lead to new ligands with novel features. A series of novel chiral ferrocenyl 6-NHCs with planar and central chirality have been designed based on the work of the others and my own research experience. The rigidity and the steric effect of the ligand will increase due to the direct fused planar ferrcenyl ring with NHC ring. The rigidity of the ligands can also be easily adjusted by the ring size of additional fused ring. The isolation and X-ray structure analysis of the new ligands and their transition metal complexes will be investigated, which are important to view their structural features. The complexes will be used as catalyst for asymmetric hydrogenation reaction and asymmetric allylic phosphination reaction.The steric effect, electronic effect as well as the impact of the planar chirality and central chirality to the reactivity, regioselectivity, and stereoselectivity in these two types of reactions will be investigated, which should provide a reference in the design of novel chiral ligands.

六元氮杂环卡宾（NHC）有独特的立体效应及电子效应；手性二茂铁基是优秀的手性配体骨架。本项目拟设计、合成一系列面手性和中心手性的二茂铁基六元NHC 配体。面手性的二茂铁平面作为氮杂环的一部分使这些NHC具有刚性和大位阻的特点；另外，通过改变并环的大小，它们还具有刚性可调的特点。进一步研究上述新型配体过渡金属络合物（Ru,Pd,Ni,Cu）的分离、单晶结构及其在不对称氢化、不对称烯丙基膦化反应中的应用。探讨立体效应、电子效应及面手性和中心手性的匹配情况对这两类反应区域选择性和对映选择性的影响，为新型配体的设计提供理论指导。

手性配体的设计合成是不对称催化的关键问题之一。不对称C-H活化反应具有原子经济性和步骤经济性的特点，是获得手性化合物的理想途径。不对称C-H活化反应也存在很大的难度和挑战。基于以上考虑本项目重点开展了手性配体和不对称C-H活化反应的探索，并将其应用到了P-中心手性膦化合物和面手性二茂铁衍生物等具有重要应用前景的化合物的合成。首先，我们探索了手性氮杂环卡宾的合成，以N,N-二甲基二茂铁基乙胺为原料经锂化、叠氮化、还原、欧联等反应获得了卡宾的合成前体。另外我们实现了二茂铁甲酰胺衍生物的分子内C-H活化去对称化反应研究，高效构建面手性二茂铁并杂环化合物；取得了高达96%的ee值。利用相同的催化体系，我们成功通过前手性膦衍生物的C-H活化去对称化反应高效的构筑了P中心手性的化合物（高达97%的ee值和99%的分离收率）。