Aggregation Studies of Complexes Containing a Chiral Lithium Amide and n-Butyllithium

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• 作者：Deyu Li ; Chengzao Sun ; Jia Liu ; Russell Hopson ; Weibin Li ; Paul G. Williard
• 刊名：Journal of Organic Chemistry
• 出版年：2008
• 出版时间：March 21, 2008
• 年：2008
• 卷：73
• 期：6
• 页码：2373 - 2381
• 全文大小：256K
• 年卷期：v.73,no.6(March 21, 2008)
• ISSN：1520-6904

文摘

A system consisting of a chiral lithium amide and n-BuLi in tol-d₈ solution was investigated with ¹H and¹³C INEPT DOSY, ⁶Li and ¹⁵N NMR, and other 2D NMR techniques. A mixed 2:1 trimeric complexwas identified as the major species as the stoichiometry approached 1.5 equiv of n-BuLi to 1 equiv ofamine compound. ¹H and ¹³C INEPT DOSY spectra confirmed this lithium aggregate in the solution.The formula weight of the aggregate, correlated with diffusion coefficients of internal references, indicatedthe aggregation number of this complex. Plots of log D_rel vs log FW are linear (r > 0.9900). ⁶Li and ¹⁵NNMR titration experiments also corroborated these results. These NMR experiments indicate that thismixed aggregate is the species that is responsible for asymmetric addition of n-BuLi to aldehydes.