四川大学冯小明团队开发出路易斯酸光氧化还原催化实现对映选择性自由基加成酮。相关研究成果发表在2022年11月22日出版的国际知名学术期刊《美国化学会杂志》。

光催化为羰基化学开辟了一个新的窗口。尽管羰基化合物发生了大量光化学反应，可见光诱导的催化不对称转化仍然难以实现，并构成了巨大的挑战。因此，开发简单、高效和经济的催化系统是化学家的理想追求。

该文中，研究人员报道了通过路易斯酸实现的光氧化催化对映选择性自由基光加成到酮上，其中原位形成的手性N，N′-二氧化物/Sc（III）-酮络合物用作临时光催化剂，以触发硅烷的单电子转移氧化，生成亲核自由基物种，包括伯、仲和叔烷基自由基，得到各种富含对映体的氮杂杂环基叔醇，其产率和对映体选择性良好至优异。电子顺磁共振（EPR）和高分辨质谱（HRMS）测量结果证明了该反应的立体控制自由基加成过程。

附：英文原文

Title: Enantioselective Radical Addition to Ketones through Lewis Acid-Enabled Photoredox Catalysis

Author: Liuzhen Hou, Yuqiao Zhou, Han Yu, Tangyu Zhan, Weidi Cao, Xiaoming Feng

Issue&Volume: November 22, 2022

Abstract: Photocatalysis opens up a new window for carbonyl chemistry. Despite a multitude of photochemical reactions of carbonyl compounds, visible light-induced catalytic asymmetric transformations remain elusive and pose a formidable challenge. Accordingly, the development of simple, efficient, and economic catalytic systems is the ideal pursuit for chemists. Herein, we report an enantioselective radical photoaddition to ketones through a Lewis acid-enabled photoredox catalysis wherein the in situ formed chiral N,N′-dioxide/Sc(III)–ketone complex serves as a temporary photocatalyst to trigger single-electron transfer oxidation of silanes for the generation of nucleophilic radical species, including primary, secondary, and tertiary alkyl radicals, giving various enantioenriched aza-heterocycle-based tertiary alcohols in good to excellent yields and enantioselectivities. The results of electron paramagnetic resonance (EPR) and high-resolution mass spectrum (HRMS) measurements provided favorable evidence for the stereocontrolled radical addition process involved in this reaction.

DOI: 10.1021/jacs.2c09691

Source: https://pubs.acs.org/doi/10.1021/jacs.2c09691