Enantioselective Inverse Electron Demand (3 + 2) Cycloaddition of Palladium-Oxyallyl Enabled by a Hydrogen-Bond-Donating Ligand.
Enantioselective Inverse Electron Demand (3 + 2) Cycloaddition of Palladium-Oxyallyl Enabled by a Hydrogen-Bond-Donating Ligand.
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DOI：
10.1021/jacs.0c11504
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发表时间：
2021-01
影响因子：
15
通讯作者：
Yin Zheng;Tian Qin;W. Zi
中科院分区：
文献类型：
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作者：
Yin Zheng;Tian Qin;W. Zi
烯丙基氧正离子与烯烃的环加成反应是构建环体系的重要转化反应。虽然氧烯丙基阳离子的（4 + 3）环加成反应已经发展得很好，但（3 + 2）环加成反应仍然很少，并且尚未开发出不对称版本。此外，因为氧烯丙基阳离子是高度亲电的，只有富电子烯烃可以用作环加成伙伴。本文报道了钯氧烯丙基物种与缺电子硝基烯烃的不对称（3 + 2）环加成反应。这种转变是通过合理设计的氢键供体配体（FeUrPhos），并通过逆电子需求途径进行。利用这种方法，我们可以组装多达三个连续的立体中心的环戊酮，具有高的对映选择性和良好的非对映选择性。
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.