Lithium hexamethyldisilazide-mediated enolizations:: Influence of triethylamine on E/Z selectivities and enolate reactivities

被引:45
作者
Godenschwager, Peter F. [1 ]
Collum, David B. [1 ]
机构
[1] Cornell Univ, Baker Lab, Dept Chem & Chem Biol, Ithaca, NY 14853 USA
关键词
D O I
10.1021/ja800250q
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Lithium hexamethyldisilazide (LiHMDS) in triethylamine (Et3N)/toluene is shown to enolize acyclic ketones and esters rapidly and with high E/Z selectivity. Mechanistic studies reveal a dimer-based mechanism consistent with previous studies of LiHMDS/Et3N. E/Z equilibration occurs when <2.0 equiv of LiHMDS are used. Studies of the aldol condensation and Ireland-Claisen rearrangement of the resulting Et3N-solvated enolates show higher and often complementary diastereoselectivities when compared with analogous reactions in THF. The Et3N-solvated enolates also display a marked (20-fold) acceleration of the Ireland-Claisen rearrangement with evidence of autocatalysis. A possible importance of amine-solvated enolates is discussed.
引用
收藏
页码:8726 / 8732
页数:7
相关论文
共 117 条