Magnesium Catalysis of Imine Hydroboration

被引：122
作者：
Arrowsmith, Merle [1 ]
Hill, Michael S. [1 ]
Kociok-Koehn, Gabriele [1 ]
机构：
[1] Univ Bath, Dept Chem, Bath BA2 7AY, Avon, England
来源：
CHEMISTRY-A EUROPEAN JOURNAL | 2013年 / 19卷 / 08期
基金：
英国工程与自然科学研究理事会;
关键词：
homogeneous catalysis; hydroboration; imines; magnesium; main group elements; CHIRAL TITANOCENE CATALYST; ASYMMETRIC HYDROGENATION; INTERMOLECULAR HYDROAMINATION; CARBONYL-COMPOUNDS; REDUCING AGENT; HYDROSILYLATION; REDUCTION; COMPLEXES; CALCIUM; KETONES;
D O I：
10.1002/chem.201203190
中图分类号：
O6 [化学];
学科分类号：
0703 ;
摘要：
The -diketiminato magnesium alkyl complex [LMgnBu] (L=CH{CMe(NDipp)}2, Dipp=diisopropylphenyl) is shown to be a highly effective precatalyst for the hydroboration of alkyl and aryl substituted aldimines and ketimines with pinacol borane (HBpin). Catalysis is proposed to occur through a sequence of MgN/BH metathesis and rate-determining MgH/NC insertion steps, a proposal strongly supported by stoichiometric studies and kinetic analysis. The reactions are observed to proceed through the intermediacy of well-defined magnesium amides, two examples of which have been isolated and structurally characterized. Mechanistic investigations suggest that the catalytic rate-determining process occurs at an isolated magnesium center and requires the presence of two molecules of the imine substrate for effective turnover. This latter observation is rationalized as a requirement for the secondary substrate molecule to displace HBpin from the coordination sphere of the catalytic magnesium center.
引用
收藏
页码：2776 / 2783
页数：8
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