Department of Chemistry, University of California, Berkeley, CA, 94720, USA.
Department of Chemistry, University of Utah, Salt Lake City, UT, 84112, USA.
Angew Chem Int Ed Engl. 2018 Jan 8;57(2):589-593. doi: 10.1002/anie.201711277. Epub 2017 Dec 12.
Reported is the first enantioselective oxidative Pummerer-type transformation using phase-transfer catalysis to deliver enantioenriched sulfur-bearing heterocycles. This reaction includes the direct oxidation of sulfides to a thionium intermediate, followed by an asymmetric intramolecular nucleophilic addition to form chiral cyclic N,S-acetals with moderate to high enantioselectivites. Deuterium-labelling experiments were performed to identify the stereodiscrimination step of this process. Further analysis of the reaction transition states, by means of multidimensional correlations and DFT calculations, highlight the existence of a set of weak noncovalent interactions between the catalyst and substrate that govern the enantioselectivity of the reaction.
本文报道了首例使用相转移催化的对映选择性氧化 Pummerer 型转化反应,以提供对映富集的含硫杂环。该反应包括将硫化物直接氧化为硫鎓中间体,然后进行不对称分子内亲核加成,以中等至高对映选择性形成手性环状 N,S-缩醛。进行了氘标记实验以确定该过程的立体选择性步骤。通过多维相关和 DFT 计算进一步分析反应过渡态,突出了催化剂和底物之间存在一组弱非共价相互作用,这些相互作用控制着反应的对映选择性。