Electrophilic Aromatic Substitutions of Aryltrifluoroborates with Retention of the BF<sub>3</sub><sup>–</sup> Group: Quantification of the Activating and Directing Effects of the Trifluoroborate Group
作者:Guillaume Berionni、Varvara Morozova、Maximilian Heininger、Peter Mayer、Paul Knochel、Herbert Mayr
DOI:10.1021/ja4017655
日期:2013.4.24
contrast to common belief, substitutions at CH positions are often faster than ipso-substitutions of the BF3K group, because BF3K activates the position attached to boron by a factor of 10(3)-10(4) while adjacent CH positions are activated by factors of 10(5)-10(6). Several reactions that have previously been interpreted as ipso-substitutions actually proceed via initial substitution at a vicinal or remote
已经研究了呋喃基、噻吩基和吲哚基三氟硼酸盐与二苯甲基鎓 (Ar2CH(+)) 和亚胺鎓 (Me2N(+)=CHR) 离子的无过渡金属反应的动力学和机制。与普遍看法相反,CH 位置的取代通常比 BF3K 基团的 ipso 取代更快,因为 BF3K 以 10(3)-10(4) 的因子激活与硼相连的位置,而相邻的 CH 位置被激活10(5)-10(6) 的因子。之前被解释为同位取代的几种反应实际上是通过在邻近或远程 CH 位置的初始取代进行的,然后是原脱硼。如果在 CH 位置的亲电取代过程中释放的质子被碱基捕获,则可以保留 BF3(-) 基团。