【摘要】 发展了一种新的超分子亚胺离子催化的策略.为了提高传统亚胺离子催化的效率并且提供一种新的不对称催化方法,最近发展了一种致力于活化亚胺离子的新催化概念,即超分子亚胺离子催化.为了扩展该策略的应用范围,在此进一步发展了该方法,使之拓展到可以同时对亚胺离子和亲核体进行双活化的超分子亚胺离子催化方法.这种新的方法可以显著提高催化剂的活性,使之前应用传统方法比较惰性的反应变得具有良好的反应性.报道的方法可以用于提高一些比较惰性反应的反应活性,也可以为设计一些新反应提供一种思路.更多还原

【Abstract】 An alternative modular strategy has been developed for hydrogen-bond-mediated supramolecular iminium catalysis(SIC). To improve the efficiency of traditional iminium ion catalysis and provide a new approach to asymmetric catalysis, we recently developed a new concept which aims to activate iminium ions. To expand the scope of SIC, we reported here a rationally designed strategy involving the dual activation of both iminium ions and the nucleophilic partner that provides new opportunities for improving the reactivity and designing new reactions. We analyzed the different reaction rates of the addition reaction of malonate to α,β-unsaturated aldehyde catalyzed by traditional iminium ion catalysis and supramolecular iminium catalysis by the means of 1H NMR monitoring of the reaction conversions and comparison of the isolated yields. Moreover, different carboxylic acids were employed in iminium catalytic Michael addition reaction of malonate to α,β-unsaturated aldehyde to test our hypothesis. General speaking, by using this novel supramolecular iminium catalysis, the enantioselectivities of the Michael addition products are excellent(93%~95%) with moderate to good yields(61%~86%), meanwhile, all these reactions were rather slow and only 33%~57% conversions were obtained even after 7 days in the presence of traditional iminium ion catalysis. Further reducing the catalyst loading to 5 mol%, the reaction proceeded smoothly to give a >90% conversion with 94% ee after 12 h. The results revealed that the use of less acidic acid which generates lower concentration of iminium ion associated with stronger anion-binding stabilized conjugate base gives faster reaction rate. The experimental results indicate a new approach for SIC which involves an anion-exchange process between anion-binding stabilized carboxylate ion and malonate. The self-assembled supramolecular system has higher reactivity, better efficiency and greater turnover numbers. This general strategy has the potential to be applied in many iminium catalytic nucleophilic addition reactions and might provide new opportunities for designing new asymmetric reactions. The further study is currently underway in our laboratory.更多还原