Research for Asymmetric Synthesis of Group 14-Element Centered Anions

含有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)曾由Brook等人报道。然而，对光学活性的锗基锂或锡基锂的关注要少得多。本文报道了以(-)-雀花碱为手性配体的新型光学活性锗基锂的研究结果。在Schlenk管中，相应的氢化物与叔丁基锂在四氢呋喃中，在半量的(-)-雀花碱的存在下反应，合成了叔丁基甲基苯基锗锂(t-BuMePhGeLi)(1)。化合物1的结构经~1H、~(7)Li和~(13)C核磁共振表征。变温核磁共振光谱观察到1-(SP)和1-(THF)_2之间的配体交换反应。聚合点为107kcal，活化能为18.0kcal/℃。用n-…重结晶成功地拆分了(-)斯马豆碱(1^*)对锗锂的光学拆分正己烷/甲苯混合溶剂较多。用X-射线衍射法测定了1^*的分子结构。结果表明，旋光性1^*的绝对构型为R构型，该方法也可用于合成旋光性锡基锂。在叔丁基甲基苯基锡基锂(t-BuMePhSnLi)(2)的外消旋混合物中加入半量的(-)-雀花碱，即可实现锡基锂的光学拆分。光学纯的锡基锂(-)-司马汀配合物2-(Sp)为无色晶体，其绝对结构经X-射线晶体分析确定为R构型，在(-)-司马汀存在下，叔丁基甲基锗(t-BuMeGeH_2)与仲丁基锂反应，得到(-)-斯巴丁基叔丁基甲基氢化锗锂(t-BuMeHGeLi，3)。3-(SP)与三苯基氯硅烷反应生成叔丁基甲基(三苯基硅基)锗(t-BuMeHGeSiPh_3)的偶联产物。得到的旋光活性硅基锗化合物的ee为48%，单晶X射线衍射仪测定其绝对结构为S构型。较少

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