Mechanistic Study on Asymmetric Oxidations with Metallosalen Complexes as Catalysts and Exploitation of New Metallosalen Complexes

金属Salen配合物催化剂不对称氧化机理研究及新型金属Salen配合物的开发

基本信息

批准号：
09440220
负责人：
KATSUKI Tsutomu
金额：
$ 8.83万
依托单位：
Kyushu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

Metallosalen Complexes are excellent catalysts for asymmetric oxene and carbene transfer reactions but our understanding of the mechanism of asymmetric induction is still immature. However, knowledge on the mechanism is indispensable for understanding the stereochemistries of the asymmetric reactions and developing new type of highly efficient asymmetric reactions.Although salen ligand had been recognized to have a planar structure, the analysis of stereochemistry in the ylide formation of sulfide using chiral (salen)cobalt complex suggested that the salen ligand had not a planar but stepped structure. This finding on the ligand-conformation was strongly supported by realizing as asymmetric epoxidation with achiral (salen)manganese complexes as catalysts in the presence of chiral axial ligands. Furthermore, X-ray analysis of chiral (salen)manganese complexes proved that the salen ligands adopt stepped conformation. Basing on these findings, we succeeded in an efficient kinetic resolution of allene compounds and asymmetric hydroxylation of benzylic C-H bonds.In addition to these results, unique asymmetric cyclopropanation was also developed by employing nitroso (salen) ruthenium complexes. Though the ruthenium complexes are catalytically inactive, photo-irradiation makes them active. Furthermore, the complexes are expected to have highly pliable structure basing on the X-ray analysis of the complex. Taking advantage of high pliability of the ruthenium complex, we could controlled the ligand conformation by choosing solvent and achieve for the first time highly cis- and enantio-selective cyclopropanation.

Metallosalen配合物是不对称氧烯和卡宾转移反应的优异催化剂，但我们对不对称诱导机制的理解仍然不成熟。然而，关于其机理的知识对于理解不对称反应的立体化学和开发新型高效不对称反应是必不可少的。尽管salen配体已被认为具有平面结构，但使用手性分子分析硫化物叶立德形成的立体化学(salen)钴配合物表明salen配体不是平面结构而是阶梯结构。关于配体构象的这一发现得到了在手性轴向配体存在下以非手性（salen）锰配合物作为催化剂实现不对称环氧化的有力支持。此外，手性(salen)锰配合物的X射线分析证明salen配体采用阶梯式构象。基于这些发现，我们成功地实现了丙二烯化合物的有效动力学拆分和苄基C-H键的不对称羟基化。除了这些结果之外，还通过使用亚硝基（salen）钌配合物开发了独特的不对称环丙烷化反应。尽管钌配合物没有催化活性，但光照射使其具有活性。此外，根据复合物的 X 射线分析，预计该复合物具有高度柔韧的结构。利用钌配合物的高柔韧性，我们可以通过选择溶剂来控制配体构象，首次实现了高度顺式和对映选择性的环丙烷化。