1. Catalytic Asymmetric Aza‐Diels–Alder Reaction of Ketimines and Unactivated Dienes.
- Author
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Zhao, Qun, Li, Yao, Zhang, Qing‐Xia, Cheng, Jin‐Pei, and Li, Xin
- Subjects
DIELS-Alder reaction ,DIOLEFINS ,IMINES ,ACID catalysts ,PHOSPHORIC acid - Abstract
The enantioselective aza‐Diels–Alder reaction is efficient for constructing chiral tetrahydropyridines, but the catalytic asymmetric aza‐Diels–Alder reaction of ketimines with unactivated dienes is still a challenging topic. Herein, guided by computational screening, a highly enantioselective aza‐Diels–Alder reaction of 2‐aryl‐3H‐indol‐3‐ones with unactivated dienes was realized by using a B(C6F5)3/chiral phosphoric acid catalyst system under mild conditions. The reaction has a broad scope with respect to both aza‐Diels–Alder reaction partners and hence offers rapid access to an array of tetrahydropyridine derivatives with pretty outcomes (up to 99 % yield, >20:1 dr and 98:2 er). The reaction is very efficient: lowering catalyst loadings for the model reaction to 0.1 mol %, enantioselectivity is still maintained. The synthetic utility was confirmed by transformations of the products. DFT calculations provide convincing evidence for the interpretation of stereoselection. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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