Heterogeneous Supramolecular Catalysis through Immobilization of Anionic M4L6 Assemblies on Cationic Polymers
Heterogeneous Supramolecular Catalysis through Immobilization of Anionic M4L6 Assemblies on Cationic Polymers
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DOI：
10.1021/jacs.0c09556
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发表时间：
2020-11-11
影响因子：
15
通讯作者：
Toste, F. Dean
中科院分区：
文献类型：
--
作者：
Miyamura, Hiroyuki;Bergman, Robert G.;Toste, F. Dean
虽然目前开发的大多数超分子催化剂通过特定的主客体相互作用以独特的选择性和活性模拟酶反应性，但在均相条件下，自然界中的酶可以在非均相条件下作为膜结合酶操作。为了发展这样一个多相体系，我们将固定化的手性超分子簇Ga（4）1（6）（2）引入到具有阳离子官能团的交联聚合物中。这些非均相超分子催化剂用于aza-Prins和aza-Cope反应，并成功地应用于连续流动反应。他们表现出很高的耐久性，并保持了很长一段时间的高营业额。与大多数多相化均相催化剂的实例形成鲜明对比，新开发的催化剂与相应的可溶性簇合物催化剂相比显示出增强的活性和稳健性。一个对映体富集的集群也被固定化，使不对称催化，和活性和对映体选择性的负载的手性催化剂保持在回收和再利用的实验过程中，并根据连续流的过程。值得注意的是，在聚合物中的铵阳离子的结构影响稳定性，反应性，和对映选择性，这是一致的假设，即在聚合物载体中的阳离子部分与簇相互作用，作为一个exohedral保护壳，从而影响它们的催化性能。
Although most of the currently developed supramolecular catalysts that emulate enzymatic reactivity with unique selectivity and activity through specific host-guest interactions work under homogeneous conditions, enzymes in nature can operate under heterogeneous conditions as membrane-bound enzymes. In order to develop such a heterogeneous system, an immobilized chiral supramolecular cluster Ga(4)1(6) (2) was introduced into cross-linked polymers with cationic functionalities. These heterogeneous supramolecular catalysts were used in aza-Prins and aza-Cope reactions and successfully applied to continuous-flow reactions. They showed high durability and maintained high turnovers for long periods of time. In sharp contrast to the majority of examples of heterogenized homogeneous catalysts, the newly developed catalysts showed enhanced activity and robustness compared to those exhibited by the corresponding soluble cluster catalyst. An enantioenriched cluster was also immobilized to enable asymmetric catalysis, and activity and enantioselectivity of the supported chiral catalyst were maintained during recovery and reuse experiments and under a continuous-flow process. Significantly, the structure of the ammonium cations in the polymers affected stability, reactivity, and enantioselectivity, which is consistent with the hypothesis that the cationic moieties in the polymer support interact with cluster as an exohedral protecting shell, thereby influencing their catalytic performance.