Insights into the origin of high activity and stability of catalysts derived from bulky, electron-rich monophosphinobiaryl ligands in the Pd-catalyzed C-N bond formation.
Insights into the origin of high activity and stability of catalysts derived from bulky, electron-rich monophosphinobiaryl ligands in the Pd-catalyzed C-N bond formation.
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DOI：
10.1021/ja037932y
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发表时间：
2003-10
影响因子：
15
通讯作者：
E. Strieter;D. Blackmond;S. Buchwald
中科院分区：
文献类型：
--
作者：
E. Strieter;D. Blackmond;S. Buchwald
本文报道了几种单膦基配体催化剂体系的动力学比较研究。膦配体的体积控制着催化活性和催化剂的活化速率，2-双环己基膦-2',4',6'-三异丙基联苯基催化剂的活性最大，活化速度最快。在催化剂活化缓慢的情况下（即使用较小的配体，如2-双环己基膦-2'-甲基联苯与Pd(OAc)2结合），在反应开始前将胺与催化剂/碱混合物搅拌，可以增加反应速率以及催化剂的活化速率。动力学同位素效应证实了催化剂的活化过程是通过β -氢化物消除途径发生的。
A comparative kinetic examination of catalyst systems based on several monophosphinobiaryl ligands is reported. The bulk of the phosphine ligand controls the catalytic activity and the rate of catalyst activation with the catalyst based on 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl providing the greatest activity and fastest activation. In the case where catalyst activation is slow (i.e., use of the smaller ligands such as 2-dicyclohexylphosphino-2'-methylbiphenyl in combination with Pd(OAc)2) stirring the amine with the catalyst/base mixture prior to the commencement of the reaction increases the reaction rate along with the rate of catalyst activation. Kinetic isotope effects established that the catalyst activation process occurs through a beta-hydride elimination pathway.