Li Deyu, Sun Chengzao, Liu Jia, Hopson Russell, Li Weibin, Williard Paul G
Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA.
J Org Chem. 2008 Mar 21;73(6):2373-81. doi: 10.1021/jo702655m. Epub 2008 Feb 23.
A system consisting of a chiral lithium amide and n-BuLi in tol-d(8) solution was investigated with (1)H and (13)C INEPT DOSY, (6)Li and (15)N NMR, and other 2D NMR techniques. A mixed 2:1 trimeric complex was identified as the major species as the stoichiometry approached 1.5 equiv of n-BuLi to 1 equiv of amine compound. (1)H and (13)C INEPT DOSY spectra confirmed this lithium aggregate in the solution. The formula weight of the aggregate, correlated with diffusion coefficients of internal references, indicated the aggregation number of this complex. Plots of log D(rel) vs log FW are linear (r > 0.9900). (6)Li and (15)N NMR titration experiments also corroborated these results. These NMR experiments indicate that this mixed aggregate is the species that is responsible for asymmetric addition of n-BuLi to aldehydes.
采用¹H和¹³C INEPT DOSY、⁶Li和¹⁵N NMR以及其他二维NMR技术，对由手性酰胺锂和正丁基锂在氘代甲苯溶液中组成的体系进行了研究。当化学计量比接近1.5当量的正丁基锂与1当量的胺化合物时，一种混合的2:1三聚体络合物被确定为主要物种。¹H和¹³C INEPT DOSY光谱证实了溶液中的这种锂聚集体。与内标扩散系数相关的聚集体分子量表明了该络合物的聚集数。log D(rel) 对log FW的图呈线性 (r > 0.9900)。⁶Li和¹⁵N NMR滴定实验也证实了这些结果。这些NMR实验表明，这种混合聚集体是导致正丁基锂对醛进行不对称加成的物种。
