Achieving High Ortho Selectivity in Aniline C–H Borylations by Modifying Boron Substituents
作者:Milton R. Smith、Ranjana Bisht、Chabush Haldar、Gajanan Pandey、Jonathan E. Dannatt、Behnaz Ghaffari、Robert E. Maleczka、Buddhadeb Chattopadhyay
DOI:10.1021/acscatal.8b00641
日期:2018.7.6
High ortho selectivity for Ir-catalyzed C–H borylations (CHBs) of anilines results when B2eg2 (eg = ethylene glycolate) is used as the borylating reagent in lieu of B2pin2, which is known to give isomeric mixtures with anilines lacking a blocking group at the 4-position. With this modification, high selectivities and good yields are now possible for various anilines, including those with groups at
当使用B 2例如2(例如=乙二醇酯)代替B 2销2时,对苯胺的Ir催化C–H硼烷基化(CHBs)具有很高的邻位选择性,这是已知的异构体混合物。苯胺在4位上缺少封闭基团。通过这种修饰,对于各种苯胺,包括在2和3位有基团的苯胺,现在可以实现高选择性和高收率。实验表明,在CHB之前生成了ArylN(H)Beg物种,并且相对于B 2 pin 2支持了邻位选择性的提高。Ir催化剂上较小的Beg配体引起的反应。来自密度泛函理论计算分析的最低能级跃迁状态(TSs)在PhN(H)Beg和Beg配体中的O原子之间具有N–H··O氢键相互作用。PhN(H)Me与B 2例如2的Ir催化CHB也是高度邻位选择性的。1 H NMR实验表明,N-硼化在CHB之前完全生成PhN(Me)Beg。具有最低吉布斯能量的TS是邻位TS,其中Beg单元的取向与联吡啶配体相反。