Chiral Zirconium Catalysts Using Multidentate BINOL Derivatives for Catalytic Enantioselective Mannich-Type Reactions; Ligand Optimization and Approaches to Elucidation of the Catalyst Structure
作者:Yoichi Ihori、Yasuhiro Yamashita、Haruro Ishitani、Shū Kobayashi
DOI:10.1021/ja053524d
日期:2005.11.1
Catalytic enantioselective Mannich-type reactions of silicon enolates with aldimines were investigated using chiral zirconium catalysts prepared from Zr(O(t)Bu)(4), N-methylimidazole, and newly designed multidentate BINOL derivatives. These new multidentate BINOL ligands were designed on the basis of an assumed transition state structure of a chiral zirconium catalyst derived from two molecules of
使用由 Zr(O(t)Bu)(4)、N-甲基咪唑和新设计的多齿 BINOL 衍生物制备的手性锆催化剂,对硅烯醇与 aldimines 的催化对映选择性曼尼希型反应进行了调查。这些新的多齿 BINOL 配体是基于从 (R)-6,6'-Br(2)-BINOL 的两个分子衍生的手性锆催化剂的假定过渡态结构设计的。不仅四齿 BINOL 4 而且三齿 BINOL 衍生物都被发现是有效的,并且获得了高对映选择性。在由三齿配体 6e 制备的最有效的锆配合物的结构研究中,进行了多次核磁共振实验和 DFT 计算。因此,阐明了活性催化剂的结构和不对称诱导的合理机制。