Tirel Emmanuel Y, Williams Nicholas H
Department of Chemistry, University of Sheffield, Sheffield S3 7HF (UK).
Chemistry. 2015 May 4;21(19):7053-6. doi: 10.1002/chem.201500619. Epub 2015 Mar 18.
Metal-ion complexes are the most effective artificial catalysts capable of cleaving phosphate diesters under mild aqueous conditions. A central strategy for making these complexes highly reactive has been to use ligand-based alcohols that are coordinated to the ion, providing an ionised nucleophile under neutral conditions but at the expense of deactivating it. We have created a highly reactive Zn complex that is 350-fold more reactive than an alcohol analogue by preventing the nucleophile binding to the metal ion. This strategy successfully delivers the benefits of efficient nucleophile delivery without strongly deactivating the metal ion Lewis acidity nor the oxyanion nucleophilicity. Varying the leaving group reveals that the transition state of the reaction is much further advanced than the reaction with hydroxide.
金属离子配合物是在温和的水性条件下能够裂解磷酸二酯的最有效的人工催化剂。使这些配合物具有高反应活性的一个核心策略是使用与离子配位的基于配体的醇，在中性条件下提供一个离子化的亲核试剂，但代价是使其失活。我们通过防止亲核试剂与金属离子结合，创造了一种反应活性比醇类似物高350倍的高反应活性锌配合物。该策略成功地实现了高效亲核试剂传递的好处，而不会强烈降低金属离子的路易斯酸性和亲氧阴离子亲核性。改变离去基团表明，该反应的过渡态比与氢氧化物的反应要先进得多。
