Cationic Multidentate Halogen-Bond Donors in Halide Abstraction Organocatalysis: Catalyst Optimization by Preorganization
作者:Stefan H. Jungbauer、Stefan M. Huber
DOI:10.1021/jacs.5b07863
日期:2015.9.23
show that the catalytic activity is based on halogen bonding using, e.g., the chlorinated derivatives as reference compounds. On the basis of these studies, halobenzimidazolium organocatalysts were then investigated. Monodentate compounds featured the same trends as the corresponding imidazolium analogues but showed a stronger catalytic activity. In order to prepare bidentate versions which are preorganized
与在有机催化中牢固建立的氢键相反,卤素键在该领域的应用仍然很少。在此,我们首次展示了阳离子卤素键供体在卤化物提取反应中的催化应用。首先,系统地测试了基于卤代吡啶鎓、卤咪唑鎓和卤化 1,2,3-三唑鎓的催化剂。与吡啶鎓化合物相比,咪唑鎓和三唑鎓盐均显示出有希望的效力。对于基于卤代咪唑鎓的有机催化剂,我们可以证明催化活性基于卤素键合,例如使用氯化衍生物作为参考化合物。在这些研究的基础上,研究了卤代苯并咪唑鎓有机催化剂。单齿化合物与相应的咪唑鎓类似物具有相同的趋势,但表现出更强的催化活性。为了制备预先组织用于阴离子结合的二齿形式,合成了一类新的刚性双(卤代苯并咪唑鎓)化合物并对其进行了结构表征。相应的顺式异构体显示出前所未有的催化效力,可以低至 0.5 mol% 用于 1-氯异色满与甲硅烷基烯醇醚的基准反应。计算证实顺式异构体可能以双齿方式与氯化物结合。各自的反异构体活性较低并且以单齿方式结合卤