Macrocycle-Enabled Counteranion Trapping for Improved Catalytic Efficiency
Macrocycle-Enabled Counteranion Trapping for Improved Catalytic Efficiency
复制标题
大环启用的抗衡阴离子捕获可提高催化效率
DOI：
10.1002/chem.201800326
复制
发表时间：
2018-03-20
影响因子：
4.3
通讯作者：
Wang, Qi-Qiang
中科院分区：
文献类型：
--
作者：
Ning, Rui;Ao, Yu-Fei;Wang, Qi-Qiang
功能性大环化合物实现的紧密的主客体结合可用于调节催化作用。虽然强冠醚-阳离子络合已广泛应用于增强配对阴离子的反应活性，但通过应用大环阴离子受体捕获抗衡阴离子以提高阳离子催化活性的互补策略仍未被探索。为了实现这一策略，合成了包含多个协同氢键位点的大环，并显示其可以紧密捕获晶体和乙腈溶液中的乙二磺酸根阴离子（K>10(6)m(-1)）。由于具有较强的结合倾向，低至0.25mol%的大环化合物的存在可以显着提高乙二磺酸催化的Povarov反应效率，而无环类似物则效果减弱。催化结果和结合研究一起表明，大环促进是通过捕获酸催化剂的反阴离子来促进底物质子化的。
The tight host-guest binding enabled by functional macrocycles can be utilized to tune catalysis. While the strong crown ether-cation complexation has been widely applied on enhancing the reactivity of the paired anion, the complementary strategy by applying a macrocyclic anion receptor to trap a counteranion to improve the cation catalytic activity remains unexplored. To realize this strategy, a macrocycle incorporating multiple cooperative H-bonding sites was synthesized and shown to tightly trap ethanedisulfonate anion in crystals and in acetonitrile solution (K>10(6)m(-1)). With the strong binding tendency, the presence of as low as 0.25mol% of the macrocycle can significantly improve the ethanedisulfonic acid-catalyzed Povarov reaction efficiency, while the acyclic analogues had diminished effect. Catalysis outcomes and binding studies taken together suggested the macrocycle promotion was through favoring the substrate protonation by trapping the counteranion of the acid catalyst.