Blum Suzanne A, Rivera Vicki A, Ruck Rebecca T, Michael Forrest E, Bergman Robert G
Department of Chemistry, University of California, Berkeley, California 94720.
Organometallics. 2005 Mar 28;24(7):1647-1659. doi: 10.1021/om049105r.
The reactions of the bis(cyclopentadienyl)(tert-butylimido)zirconium complex (Cp(2)Zr=N-t-Bu)(THF) (1) with epoxides, aziridines, and episulfides were investigated. Heterocycles without accessible beta-hydrogens undergo insertion/protonation of the C-X bond to produce 1,2-amino alcohols (X = O) and 1,2-diamines (X = NR), whereas heterocycles with accessible beta-hydrogens undergo elimination/protonation to produce allylic alcohols (X = O) and allylic sulfides (X = S). Mechanistic investigations support a stepwise pathway with zwitterionic intermediates for the first reaction class and a concerted pathway for the second reaction class. Additionally, the feasibility of chirality transfer from the planar-chiral ebthi (ebthi = ethylenebis(tetrahydroindenyl)) ligand was demonstrated with a chiral analogue, (ebthi)-Zr=NAr(THF) (Ar = 2,6-dimethylphenyl), 2, through the diastereoselective ring opening of meso epoxides.
研究了双（环戊二烯基）（叔丁基亚氨基）锆配合物（Cp₂Zr=N-t-Bu）（THF）（1）与环氧化物、氮丙啶和环硫化物的反应。没有可及β-氢的杂环发生C-X键的插入/质子化反应，生成1,2-氨基醇（X = O）和1,2-二胺（X = NR），而有可及β-氢的杂环发生消除/质子化反应，生成烯丙醇（X = O）和烯丙基硫化物（X = S）。机理研究支持第一类反应通过两性离子中间体的分步途径，以及第二类反应的协同途径。此外，通过手性类似物（ebthi）-Zr=NAr（THF）（Ar = 2,6-二甲基苯基），2，通过内消旋环氧化物的非对映选择性开环，证明了从平面手性ebthi（ebthi = 亚乙基双（四氢茚基））配体进行手性转移的可行性。
