B(C 6 F 5 ) 3 /Chiral Phosphoric Acid Catalyzed Ketimine–Ene Reaction of 2‐Aryl‐3 H ‐indol‐3‐ones and α‐Methylstyrenes
| Autor: | Yao Li, Qing-Xia Zhang, Cheng-Jun Liu, Xin Li, Jin-Pei Cheng, Jie Wang, Chen Yang |
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| Rok vydání: | 2020 |
| Předmět: |
010405 organic chemistry
Enantioselective synthesis General Chemistry General Medicine 010402 general chemistry 01 natural sciences Medicinal chemistry Catalysis 0104 chemical sciences chemistry.chemical_compound chemistry Organocatalysis Stereoselectivity Reactivity (chemistry) Organic synthesis Phosphoric acid Ene reaction |
| Zdroj: | Angewandte Chemie. 132:4580-4586 |
| ISSN: | 1521-3757 0044-8249 |
| DOI: | 10.1002/ange.201915226 |
| Popis: | The enantioselective ketimine-ene reaction is one of the most challenging stereocontrolled reaction types in organic synthesis. In this work, catalytic enantioselective ketimine-ene reactions of 2-aryl-3H-indol-3-ones with α-methylstyrenes were achieved by utilizing a B(C6 F5 )3 /chiral phosphoric acid (CPA) catalyst. These ketimine-ene reactions proceed well with low catalyst loading (B(C6 F5 )3 /CPA=2 mol %/2 mol %) under mild conditions, providing rapid and facile access to a series of functionalized 2-allyl-indolin-3-ones with very good reactivity (up to 99 % yield) and excellent enantioselectivity (up to 99 % ee). Theoretical calculations reveal that enhancement of the acidity of the chiral phosphoric acid by B(C6 F5 )3 significantly reduces the activation free energy barrier. Furthermore, collective favorable hydrogen-bonding interactions, especially the enhanced N-H⋅⋅⋅O hydrogen-bonding interaction, differentiates the free energy of the transition states of CPA and B(C6 F5 )3 /CPA, thereby inducing the improvement of stereoselectivity. |
| Databáze: | OpenAIRE |
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