State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China.
J Am Chem Soc. 2021 Jan 20;143(2):1038-1045. doi: 10.1021/jacs.0c11504. Epub 2021 Jan 6.
Cycloaddition reactions between oxyallyl cations and alkenes are important transformations for the construction of ring systems. Although (4 + 3) cycloaddition reactions of oxyallyl cations are well-developed, (3 + 2) cycloadditions remain rare, and an asymmetric version has not yet been developed. Moreover, because oxyallyl cations are highly electrophilic, only electron-rich olefins can be used as cycloaddition partners. We herein report a method for enantioselective (3 + 2) cycloaddition reactions between palladium-oxyallyl species and electron-deficient nitroalkenes. This transformation was enabled by a rationally designed hydrogen-bond-donating ligand (FeUrPhos) and proceeded via an inverse electron demand pathway. Using this method, we could assemble cyclopentanones with up to three contiguous stereocenters with high enantioselectivity and good to excellent diastereoselectivity.
氧杂环丙烯阳离子与烯烃的环加成反应是构建环体系的重要转化。尽管（4 + 3）氧杂环丙烯阳离子环加成反应已经很成熟，但（3 + 2）环加成反应仍然很少见，并且尚未开发出不对称版本。此外，由于氧杂环丙烯阳离子具有高亲电性，因此只能使用富电子烯烃作为环加成伙伴。我们在此报告了一种钯-氧杂环丙烯物种与缺电子硝基烯烃之间对映选择性（3 + 2）环加成反应的方法。这种转化是通过合理设计的氢键供体配体（FeUrPhos）实现的，并通过反电子需求途径进行。使用这种方法，我们可以高对映选择性和良好到优秀的非对映选择性构建具有多达三个连续立体中心的环戊酮。
