Insight into the Role of the Counteranion of an Imidazolium Salt in Organocatalysis: A Combined Experimental and Computational Study
作者:Siping Wei、Xi-Guang Wei、Xiaoyu Su、Jingsong You、Yi Ren
DOI:10.1002/chem.201002839
日期:2011.5.16
initiate a combined experimental and computational investigation of the NHC‐catalyzed ring‐closing reactions of 4‐(2‐formylphenoxy)but‐2‐enoate derivatives 1 to uncover the relationship between the counteranion of an azolium salt, the nucleophilicity and basicity of the carbene species, and the catalytic performance of the carbene species by taking imidazolium salts IPr⋅HX (X=counteranion, IPr=1,3‐bis(2
N-杂环卡宾(NHC)可以用作反应性很强的亲核催化剂,并具有很强的碱性。在这里,我们开始对NHC催化的4-(2-甲酰基苯氧基)丁-2-烯酸酯衍生物1的闭环反应进行实验和计算的组合研究,以揭示偶氮盐的抗衡阴离子,亲核性和碱性之间的关系。卡宾物种,并且通过取卡宾物种的催化性能的咪唑鎓盐的IPr ⋅以HX(X =抗衡阴离子,IPr = 1,3-双(2,6-二异丙基苯基)咪唑-2-亚基)为代表预催化剂。通过使用DFT计算研究了IPr介导的闭环反应的合理机制。氢接受能力,分配为知识产权的抗衡阴离子的碱性⋅ HX和通过DFT计算评价,与知识产权C2的去质子化的速率相关⋅ HX,这可以通过自由卡宾的形成在捕获被监视原位含元素硫。C2的知识产权去质子⋅具有更碱性阴离子的HX会产生更高浓度的游离卡宾,反之亦然。在相对较低的浓度下,IPr倾向于表现出亲核特性以诱导分子内Stetter反应。在相对较高的浓度下,