Analysis of an Asymmetric Addition with a 2:1 Mixed Lithium Amide/n-Butyllithium Aggregate
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- 作者：Jia Liu ; Deyu Li ; Chengzao Sun ; Paul G. Williard
- 刊名：Journal of Organic Chemistry
- 出版年：2008
- 出版时间：June 6, 2008
- 年：2008
- 卷：73
- 期：11
- 页码：4045 - 4052
- 全文大小：879K
- 年卷期：v.73,no.11(June 6, 2008)
- ISSN：1520-6904
文摘
A 2:1 lithium amide/n-butyllithium aggregate 1 is investigated as an asymmetric addition template in hydrocarbon solvents. Several different chiral lithium amides were synthesized from L-valine and tested in the asymmetric addition of n-BuLi to various aldehydes. Enantiomeric excesses up to 83% were obtained in the case of the addition of n-BuLi to pivaldehyde at −116 °C in pentane. 1H and 13C INEPT DOSY were utilized to characterize a new trimeric complex 12 between 2 equiv of lithium amide and 1 equiv of lithium alkoxide. This mixed aggregate strongly indicates the possibility of product-induced chirality inhibition that is detrimental to the enantioselectivity of asymmetric addition reaction.