Yang Liangkun, Li Wang-Yuren, Hou Liuzhen, Zhan Tangyu, Cao Weidi, Liu Xiaohua, Feng Xiaoming
Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University Chengdu 610064 China
Chem Sci. 2022 Jun 22;13(29):8576-8582. doi: 10.1039/d2sc02721f. eCollection 2022 Jul 29.
A diastereo- and enantioselective photoenolization/Mannich (PEM) reaction of -alkyl aromatic ketones with benzosulfonimides was established by utilizing a chiral ,'-dioxide/Ni(OTf) complex as the Lewis acid catalyst. It afforded a series of benzosulfonamides and the corresponding ring-closure products, and a reversal of diastereoselectivity was observed through epimerization of the benzosulfonamide products under continuous irradiation. On the basis of the control experiments, the role of the additive LiNTf in achieving high stereoselectivity was elucidated. This PEM reaction was proposed to undergo a direct nucleophilic addition mechanism rather than a hetero-Diels-Alder/ring-opening sequence. A possible transition state model with a photoenolization process was proposed to explain the origin of the high level of stereoinduction.
通过使用手性α，α'-二氧化物/Ni(OTf)₂配合物作为路易斯酸催化剂，建立了α-烷基芳基酮与苯磺酰亚胺的非对映和对映选择性光烯醇化/曼尼希（PEM）反应。该反应得到了一系列苯磺酰胺及其相应的环化产物，并且在连续照射下通过苯磺酰胺产物的差向异构化观察到了非对映选择性的反转。基于对照实验，阐明了添加剂LiNTf₂在实现高立体选择性方面的作用。该PEM反应被认为经历直接亲核加成机理而非杂环狄尔斯-阿尔德/开环序列。提出了一个具有光烯醇化过程的可能过渡态模型来解释高立体诱导水平的起源。
