The diastereoselective and enantioselective substitution reactions of an isoindoline–borane complex
作者:Azhar Ariffin、Alexander J. Blake、Mark R. Ebden、Wan-Sheung Li、Nigel S. Simpkins、David N. A. Fox
DOI:10.1039/a904788c
日期:——
The alkylation of N-methylisoindolineâborane complex, using nBuLi in THF is diastereoselective, the substitution occurring predominantly syn to the borane group. Use of the sBuLiâsparteine reagent mixture in Et2O changes the diastereoselectivity observed and enables the reaction to be conducted enantioselectively, giving the chiral isoindolineâborane complexes in up to 89% ee. The relative and absolute configurations of the chiral products were established by X-ray structure determinations and NMR studies. The new asymmetric process is shown to be an enantioselective deprotonation reaction, and the intermediate organolithium is shown to be epimerisable.
使用nBuLi在THF中对N-甲基异吲哚啉-硼烷复合物进行烷基化反应具有立体选择性,取代反应主要发生在硼烷基团的syn侧。使用sBuLi-sparteine试剂混合物在Et2O中改变了观察到的立体选择性,并使反应能够进行对映选择性反应,生成手性异吲哚啉-硼烷复合物,最高可达89% ee。通过X射线结构测定和NMR研究确定了手性产物的相对和绝对构型。新的不对称过程被证明是一种对映选择性的脱质子反应,中间体有机锂显示出外消旋化的性质。