Catalytic Enantioselective <i>m</i><i>eso</i>-Epoxide Ring Opening Reaction with Phenolic Oxygen Nucleophile Promoted by Gallium Heterobimetallic Multifunctional Complexes
作者:Shigeki Matsunaga、Jagattaran Das、Jochen Roels、Erasmus M. Vogl、Noriyoshi Yamamoto、Takehiko Iida、Kentaro Yamaguchi、Masakatsu Shibasaki
DOI:10.1021/ja993650f
日期:2000.3.1
catalytic enantioselective meso-epoxide ring opening reaction with phenolic oxygen nucleophile (4-methoxyphenol) is described for the first time herein. This reaction was first found to be promoted by (R)-GaLB (Ga = gallium, L = lithium, B = (R)-BINOL), giving a variety of epoxide opening products in good to high ee (67−93% ee). However, chemical yield was only modest (yield 31−75%), despite the use of more
本文首次描述了与酚氧亲核试剂(4-甲氧基苯酚)的催化对映选择性内消旋环氧化物开环反应。该反应首先被发现由 (R)-GaLB(Ga = 镓,L = 锂,B = (R)-BINOL)促进,得到各种环氧化物开环产物,具有良好到高 ee(67-93% ee) )。然而,尽管使用了超过 20 mol% 的 GaLB,但化学产率只是适度的(产率 31-75%)。这是由于 BINOL 和 4-甲氧基苯酚之间发生了不希望的配体交换,导致了 GaLB 的去络合。研究了各种已知手性配体如6,6'-双((三乙基甲硅烷基)乙炔基)-BINOL和H8-BINOL的应用,但未获得令人满意的结果。为了克服这个问题,已经开发了一种在接头中含有配位氧原子的新型连接 BINOL。通过在 GaLB 中连接两个 BINOL 单元,Ga 复合物的稳定性大大提高。使用 3−10 mol % (R,R)-Ga-Li-linked-BINOL