Jacobson Madeleine A, Keresztes Ivan, Williard Paul G
Department of Chemistry, Brown University, Providence, RI 02912, USA.
J Am Chem Soc. 2005 Apr 6;127(13):4965-75. doi: 10.1021/ja0479540.
N-Lithio-N-(trialkylsilyl)allylamines can be deprotonated in the presence of ethereal solvents exclusively at the cis-vinylic position to yield 3,N-dilithio-N-(trialkylsilyl)allylamines under mild conditions. Low temperature (1)H and (7)Li NMR ((1)H NOESY, TOCSY, (1)H/(7)Li HSQC, and DO-NMR) studies on the solution structure of 3,N-dilithio-N-(tert-butyldimethylsilyl)allylamine identified three major aggregates in THF (monomer, dimer and tetramer), but the aggregate structures failed to explain the solvent dependence and regiochemical outcome of the reaction. Low temperature (1)H NMR (NOESY, TOCSY, DO-NMR) studies on the solution structure of N-lithio-N-(tert-butyldimethylsilyl)allylamine in the presence of nBuLi identified amide/nBuLi mixed aggregates in both the ethereal solvent THF (1:1 dimer) and the hydrocarbon solvent toluene (1:3 tetramer). Addition of 2 equiv of THF to toluene solutions induces the formation of the same THF solvated 1:1 dimer as observed in neat THF. NMR evidence suggests that in THF the mixed aggregate has close contact between the olefin and the beta-CH(2) of nBuLi, while in the absence of THF, the allyl chain appears to be pointed away from the nearest nBuLi residues.
N-锂代-N-（三烷基甲硅烷基）烯丙胺在醚类溶剂存在下，仅能在顺式乙烯基位置去质子化，从而在温和条件下生成3, N-二锂代-N-（三烷基甲硅烷基）烯丙胺。对3, N-二锂代-N-（叔丁基二甲基甲硅烷基）烯丙胺溶液结构进行的低温¹H和⁷Li NMR（¹H NOESY、TOCSY、¹H/⁷Li HSQC和DO-NMR）研究确定了在四氢呋喃（THF）中有三种主要聚集体（单体、二聚体和四聚体），但这些聚集体结构无法解释该反应的溶剂依赖性和区域化学结果。对在正丁基锂存在下的N-锂代-N-（叔丁基二甲基甲硅烷基）烯丙胺溶液结构进行的低温¹H NMR（NOESY、TOCSY、DO-NMR）研究表明，在醚类溶剂THF（1:1二聚体）和烃类溶剂甲苯（1:3四聚体）中均存在酰胺/正丁基锂混合聚集体。向甲苯溶液中加入2当量的THF会诱导形成与纯THF中观察到的相同的THF溶剂化1:1二聚体。NMR证据表明，在THF中，混合聚集体中烯烃与正丁基锂的β-CH₂之间有紧密接触，而在没有THF的情况下，烯丙基链似乎指向远离最近的正丁基锂残基的方向。
