Research for Asymmetric Synthesis of Group 14-Element Centered Anions

含不对称锗原子的光学活性有机锗化合物（甲基-1-萘基苯基锗及其衍生物）先前由Brook等人报道。然而，对光学活性的锗锂或锡锂的关注要少得多。本文报道了一种以(-)-sparteine为手性配体的新型光学活性锗锂的研究结果。在Schlenk管中，将相应的氢日耳曼与叔丁基锂在THF中反应，并加入半量的(-)-sparteine，制备了叔丁基甲基苯基germyllithium (t-BuMePhGeLi)(1)。化合物1用^1H， ^7Li和^13C核磁共振谱进行了表征。用变温核磁共振光谱法观察了1-(sp)与1-(THF)_2之间的配体交换反应。聚结点为107℃，计算得到自由活化能为18.0 kcal/mol。用（-）sparteine（1^*）在正己烷/甲苯混合溶剂中重结晶，成功地分离了锗锂。用x射线衍射测定了1^*的分子结构。因此，光活性1^*的绝对构型为R构型。该方法也可用于合成光学活性的锡锂。在叔丁基甲基苯基锡锂的外消旋混合物（t-BuMePhSnLi）中加入半量的(-)-sparteine就成功地进行了锡锂的光学分辨(2)。得到光学纯净的锡锂(-)-sparteine配合物2-(sp)为无色晶体，x射线晶体学测定其绝对结构为R构型。在(-)-sparteine存在下，叔丁基甲基日耳曼（t-BuMeGeH_2）与仲丁基锂（t-BuMeGeH_2）定量反应得到叔丁基甲基氢锗锂（t-BuMeHGeLi, 3）的(-)-sparteine配合物。将3-(sp)加入到三苯基氯硅烷中，得到了三苯基硅基叔丁基甲基锗（t-BuMeHGeSiPh_3）的偶联产物。所得的硅germane的光活性为48%，主产物的绝对结构经单晶x射线衍射确定为S型。少

Optically active organic germanium compounds bearing asymmetric germanium atom (methyl-1-naphtylphenylgermane and its derivatives) was previously reported by Brook et.al. However, far less attention has been devoted to optically active germyllithium or stannyllithium species. We report herein the results of a study of novel optically active germyllithium, using (-)-sparteine as a chiral ligand.In the Schlenk tube, tert-butylmethylphenylgermyllithium (t-BuMePhGeLi) (1) was prepared by the reaction of the corresponding hydrogermane with tert-butyllithium in THF in the presence of half amounts of (-)-sparteine. The compound of 1 was characterized by ^1H, ^7Li and ^13C NMR spectra. The ligand-exchange reaction between 1-(sp) and 1-(THF)_2 was observed by variable-temperature NMR spectroscopy. The coalescence point was 107℃, and free energy of activation was calculated to be 18.0 kcal/mol. Optical resolution of germyllithium with (-)sparteine (1^*) was succeeded by recrystallization from n- … More hexane / toluene mixed solvent. The molecular structure of 1^* was determined by X-ray diffraction. As a result, absolute configuration of optically active 1^* was R configuration.This method could also be applied to synthesis of optically active stannyllithium. Optical resolution of stannyllithium was succeeded by only addtion of half amount of (-)-sparteine into the racemic mixture of tert-butylmethylphenylstannyllithium (t-BuMePhSnLi) (2). The optically pure stannyllithium (-)-sparteine complex 2-(sp) was obtained as colorless crystals and its absolute structure had R configuration determined by X-ray crystallography.In the presence of (-)-sparteine, tert-butylmethylgermane (t-BuMeGeH_2) was reacted with sec-butyllithium to give a (-)-sparteine complex of tert-butylmethylhydrogermyllithium (t-BuMeHGeLi, 3), quantitatively. 3-(sp) was added to triphenylchlorosilane to yield a coupling product of tert-butylmethyl (triphenylsilyll germane (t-BuMeHGeSiPh_3). The resulting optically active silylgermane shows 48%ee, and the absolute structure of the main product was determined by a single crystal X-ray diffraction to be S configuration. Less