Long-Range Effects in the Metalation/Boronation of Functionalized 1,4-Dihalobenzenes
作者:Sergiusz Luliński、Janusz Serwatowski、Anna Zaczek
DOI:10.1002/ejoc.200600541
日期:2006.11
and trialkyl borate B(OR)3 (R = Et, iPr) as the electrophile. It was demonstrated that sufficient steric hindrance precludes effective ortho-lithiation at the 3-position. In such cases, a strong meta-directing effect of an oxygen- or sulfur-based substituent (OMe, OSiMe3, SMe), resulting in the preferred formation of 2,6-disubstituted 1,4-dihalobenzenes was observed. Moreover, competition experiments
使用二异丙基氨基锂 (LDA) 作为金属化剂和硼酸三烷基酯 B(OR)3 (R = Et, iPr) 作为亲电子试剂。结果表明,足够的位阻阻止了 3 位的有效正锂化。在这种情况下,观察到基于氧或硫的取代基(OMe、OSiMe3、SMe)的强间位导向效应,导致优选形成 2,6-二取代的 1,4-二卤代苯。此外,还进行了使用 2,3-双功能 1,4-二卤代苯的竞争实验,以确定羧酸盐或氟与甲氧基竞争的相对间位导向能力。2-(二甲氧基甲基)-1,4-二卤代苯 (Hal = Cl, Br) 的金属化过程具有显着的支撑效应。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)