Wageling Nicholas B, Decato Daniel A, Berryman Orion B
Department of Chemistry and Biochemistry, University of Montana, Missoula MT, USA.
Supramol Chem. 2018;30(12):1004-1010. doi: 10.1080/10610278.2018.1515488. Epub 2018 Sep 11.
The study of hydrogen bonding organocatalysis is rapidly expanding. Much research has been directed at making catalysts more active and selective, with less attention on fundamental design strategies. This study systematically increases steric hindrance at the active site of pH switchable urea organocatalysts. Incorporating strong intramolecular hydrogen bonds from protonated pyridines to oxygen stabilizes the active conformation of these ureas thus reducing the entropic penalty that results from substrate binding. The effect of increasing steric hindrance was studied by single crystal X-ray diffraction and by kinetics experiments of a benchmark reaction.
氢键有机催化的研究正在迅速扩展。许多研究致力于使催化剂更具活性和选择性，而对基本设计策略的关注较少。本研究系统地增加了pH可切换脲有机催化剂活性位点的空间位阻。引入从质子化吡啶到氧的强分子内氢键可稳定这些脲的活性构象，从而减少底物结合产生的熵罚。通过单晶X射线衍射和基准反应的动力学实验研究了增加空间位阻的效果。
