近日，南开大学的资伟伟课题组通过给氢键配体实现了钯-氧杂烯丙基的手性逆电子需求(3+2)环加成反应。该项研究成果发表在2021年1月6日出版的《美国化学会志》上。

研究人员报道了一种对映选择性(3+2)环加成反应，该反应发生在钯-氧杂烯丙基和缺电子的硝基烯之间。该反应是通过一个理性设计的给氢键配体（FeUrPhos）、以逆电子需求的通路发生的。利用这一方法，研究人员可以构建多达三个连续手性中心的环戊酮类分子，且对映和非对映选择性都很高。

据介绍，氧杂烯丙基阳离子与烯烃之间的环加成反应是构建环系统的重要途径。虽然氧杂烯丙基阳离子的(4+3)环加成反应已较为成熟，其(3+2)环加成反应依旧较为罕见，且之前尚未有其非对称版本的报道。此外，由于氧杂烯丙基阳离子高度亲电，只有富电子的烯烃可被用作环加成对象。

附：英文原文

Title: Enantioselective Inverse Electron Demand (3 + 2) Cycloaddition of Palladium-Oxyallyl Enabled by a Hydrogen-Bond-Donating Ligand

Author: Yin Zheng, Tianzhu Qin, Weiwei Zi

Issue&Volume: January 6, 2021

Abstract: 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.

DOI: 10.1021/jacs.0c11504

Source: https://pubs.acs.org/doi/10.1021/jacs.0c11504