A Stable N-Heterocyclic Carbene Organocatalyst for Hydrogen/Deuterium Exchange Reactions between Pseudoacids and Deuterated Chloroform
作者:Fabien Perez、Yajun Ren、Thomas Boddaert、Jean Rodriguez、Yoann Coquerel
DOI:10.1021/jo502578x
日期:2015.1.16
It was observed that the stable and commercially available N-heterocyclic carbene (NHC) 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, the so-called IDipp, catalyzes hydrogen/deuterium exchange reactions between pseudoacids and chloroform-d1, while the analogous saturated NHC 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene, the so-called SIMes, is inefficient for the same transformation. Experimental
据观察,稳定的和可商购的N-杂环卡宾(NHC)1,3-双(2,6-二异丙基苯基)咪唑-2-亚烷基,即所谓的IDipp,催化假酸和氯仿之间的氢/氘交换反应。 - d 1,而类似的饱和NHC 1,3-双(2,4,6-三甲基苯基)咪唑啉-2-亚基,即所谓的SIMes,对于相同的转化效率低下。DFT的实验和计算研究表明,这些反应性差异可归因于相应的偶氮三氯甲基阴离子对的相对稳定性:在前一种情况下,络合物向离子的解离方向发展,从而生成芳族偶氮阳离子和碱性三氯甲基阴离子,在后一种情况下,它是通过离子重组而演化的,从而使正式的卡宾C–H插入到氯仿的C–H键中。这些结果为Wanzlick,Arduengo,K a,DMSO = 14-19)与氯仿-d 1。