Isoprene-Mediated Lithiation of 1-Alkylimidazoles: Chiral Induction of the Alkyl Substituent
作者:Isidro M. Pastor、Rosario Torregrosa、Miguel Yus
DOI:10.2174/157017810791514850
日期:2010.7.1
The isoprene-mediated lithiation of imidazoles bearing a secondary alkyl substituent at the nitrogen (7, 8 and 13) and the subsequent nucleophilic addition to different electrophiles allows the preparation of the corresponding 2- functionalized imidazoles 10, 11 and 14. The presence of a stereogenic center in the alkyl substituent induces diastereoselection during the nucleophilic addition step with a prochiral electrophile (i.e. pivalaldehyde), producing the expected imidazole derivative with excellent overall yield, but low de (up to 26%).
通过异戊二烯介导的具有氮上二级烷基取代基的咪唑(7、8和13)的锂化反应,随后对不同亲电试剂进行亲核加成,可以制备相应的2-功能化咪唑10、11和14。烷基取代基中立体中心的的存在导致在亲核加成步骤中对消旋化亲电试剂(如三甲基乙醛)产生非对映选择性,生成了预期的咪唑衍生物,总产率很高,但对映体过量率较低(高达26%)。