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B(C 6 F 5 ) 3 /Chiral Phosphoric Acid Catalyzed Ketimine-Ene Reaction of 2-Aryl-3H-indol-3-ones and α-Methylstyrenes.
- Source :
-
Angewandte Chemie (International ed. in English) [Angew Chem Int Ed Engl] 2020 Mar 09; Vol. 59 (11), pp. 4550-4556. Date of Electronic Publication: 2020 Jan 29. - Publication Year :
- 2020
-
Abstract
- 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(C <subscript>6</subscript> F <subscript>5</subscript> ) <subscript>3</subscript> /chiral phosphoric acid (CPA) catalyst. These ketimine-ene reactions proceed well with low catalyst loading (B(C <subscript>6</subscript> F <subscript>5</subscript> ) <subscript>3</subscript> /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(C <subscript>6</subscript> F <subscript>5</subscript> ) <subscript>3</subscript> 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(C <subscript>6</subscript> F <subscript>5</subscript> ) <subscript>3</subscript> /CPA, thereby inducing the improvement of stereoselectivity.<br /> (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)
Details
- Language :
- English
- ISSN :
- 1521-3773
- Volume :
- 59
- Issue :
- 11
- Database :
- MEDLINE
- Journal :
- Angewandte Chemie (International ed. in English)
- Publication Type :
- Academic Journal
- Accession number :
- 31943586
- Full Text :
- https://doi.org/10.1002/anie.201915226