Liu Fayu, Guo Yanqi, Lu Weidong, Zhao Xiaowei, Yin Yanli, Jiang Zhiyong
Pingyuan Laboratory, School of Chemistry and Chemical Engineering, Henan Normal University Xinxiang Henan 453007 P. R. China
College of Pharmacy, Henan University Kaifeng Henan 475004 P. R. China.
Chem Sci. 2025 May 9. doi: 10.1039/d5sc01583a.
Chiral hydrogen-bonding catalysis has been successfully applied in a wide range of asymmetric photocatalytic radical-based reactions. However, it faces intrinsic challenges in the reactions that rely on oxidative quenching to initiate transformations. A critical issue arises from the formation of anionic side intermediates, which preferentially interact with protons from chiral catalysts, undermining the essential enantiocontrol required for effective product formation. In this study, we demonstrate that creating energy transfer instead of single-electron transfer to trigger these transformations presents a promising solution. As a proof-of-concept, we report the first photocatalytic spirocyclization of olefinic sulfonyl oximes with vinyl azides, furnishing a diverse array of spiroaminals with high yields (up to 94%) and enantioselectivities (up to 99% ee). The success of this method hinges on employing a sulfonyl group as an -protective group for oximes, which facilitates energy transfer as an alternative mechanism to initiate the transformation. This approach not only enhances reactivity and chemoselectivity but also creates an optimal environment for enantiocontrol. The synthetic significance of this work is underscored by the establishment of these products as a novel class of chiral ligands, with preliminary studies indicating their effectiveness in asymmetric alkynylation reactions.
手性氢键催化已成功应用于广泛的基于光催化自由基的不对称反应中。然而，在依赖氧化猝灭来引发转化的反应中，它面临着内在的挑战。一个关键问题源于阴离子侧中间体的形成，这些中间体优先与手性催化剂中的质子相互作用，破坏了有效生成产物所需的基本对映体控制。在本研究中，我们证明通过产生能量转移而非单电子转移来触发这些转化是一种很有前景的解决方案。作为概念验证，我们报道了烯基磺酰肟与乙烯基叠氮化物的首例光催化螺环化反应，以高产率（高达94%）和对映选择性（高达99% ee）提供了多种螺环胺。该方法的成功取决于使用磺酰基作为肟的 - 保护基团，这有利于能量转移作为引发转化的替代机制。这种方法不仅提高了反应性和化学选择性，还为对映体控制创造了最佳环境。通过将这些产物确立为一类新型手性配体，强调了这项工作的合成意义，初步研究表明它们在不对称炔基化反应中有效。
