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Synfacts 2007(9): 0992-0992
DOI: 10.1055/s-2007-968881
DOI: 10.1055/s-2007-968881
Organo- and Biocatalysis
© Georg Thieme Verlag Stuttgart · New York
Brønsted Acid Catalyzed Friedel-Crafts Reaction
Y.-X. Jia, J. Zhong, S.-F. Zhu, C.-M. Zhang, Q.-L. Zhou*
Nankai University, Tianjin, P. R. of China
Further Information
Publication History
Publication Date:
23 August 2007 (online)
Significance
An organocatalytic asymmetric Friedel-Crafts reaction of indoles 2 with α-aryl enamides 1 catalyzed by the chiral phosphoric acid TRIP, which was previously introduced by the List and Akiyama groups, is described. Chiral amines 3 bearing quaternary carbon atoms were obtained in high yields and enantioselectivities. Enamides 1 are in equilibrium with their corresponding ketimines, which can subsequently be protonated by phosphoric acid 4. Additionally, a hydrogen bond is assumed to be formed between the N-H of indole 2 and phosphoric acid 4. This hypothesis is supported by the fact that both N-methylated enamides 1 and indoles 2 are poor substrates.