Substitution of Hydroxybiaryls via Directed <i>o</i><i>rtho</i>-Lithiation of <i>N</i>-Silylated <i>O</i>-Aryl <i>N</i>-Isopropylcarbamates
作者:Matthias Kauch、Victor Snieckus、Dieter Hoppe
DOI:10.1021/jo0506938
日期:2005.9.1
Herein we report regioselective substitution reactions of a series of 2- and 3-hydroxybiaryls including BINOL via a new directed ortho-metalation procedure. O-Aryl N-isopropylcarbamates, conveniently prepared from phenols and isopropyl isocyanate, are temporarily and in situ N-protected by means of silyl triflates to form stable intermediates for low temperature lithiation reactions using butyllithium/TMEDA
本文我们报告了一系列的2-和3- hydroxybiaryls包括通过新定向BINOL的区域选择性取代反应邻-metalation过程。方便地由苯酚和异氰酸异丙酯制备的O-芳基N-异丙基氨基甲酸酯通过使用丁基锂/ TMEDA在乙醚中的甲硅烷基三氟甲磺酸酯进行临时和原位N-保护,以形成用于低温锂化反应的稳定中间体。所得的芳基锂有效地被各种亲电试剂取代,从而以高收率提供官能化的联芳基。ñ-在水处理过程中已经发生了甲硅烷基化反应。氨基甲酸酯随后脱保护为相应的酚的过程迅速且以定量收率进行。产物中甚至敏感的取代基(例如,CO 2 Me,CHO,SiMe 3,I)也可以在温和的碱性条件下保存,这对于氨基甲酸酯的裂解已被确定。此外,还证明了邻位取代产物在常见的交叉偶联反应中进一步形成C-C键的应用。