Organocatalytic asymmetric friedel-crafts alkylation of indoles with simple α,β-unsaturated ketones

Organic Letters

Volumn 9, Issue 7, 2007, Pages 1403-1405

  Bartoli, Giuseppe ^a   Bosco, Marcella ^a   Carlone, Armando ^a   Pesciaioli, Fabio ^a   Sambri, Letizia ^a   Melchiorre, Paolo ^a  

^a UNIVERSITY OF BOLOGNA   (Italy)

Author keywords

[No Author keywords available]

Indexed keywords

AMINE; IMINE; INDOLE DERIVATIVE; KETONE;

ALKYLATION; ARTICLE; CATALYSIS; CHEMICAL STRUCTURE; CHEMISTRY; STEREOISOMERISM; SYNTHESIS;

ALKYLATION; AMINES; CATALYSIS; IMINES; INDOLES; KETONES; MOLECULAR STRUCTURE; STEREOISOMERISM;

EID: 34147174295     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol070309o     Document Type: Article

References (34)

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21. In this report, an initial attempt to perform an asymmetric version using the MacMillan second-generation imidazolidinone afforded poor selectivity (28% ee). Recently, a low selective (up to 29 % ee) addition of indole to chalcone promoted by D-camphorsulfonic acid was reported. See: (b) Zhou, W.; Xu, L.-W.: Li, L.; Yang, L.; Xia, C.-G. Eur. J. Org. Chem. 2006, 5225-5227. See also ref 13.
22. During our studies, the successful application of a similar ACDC tactic for the enantioselective hydrogenation of simple enones was described. See: (a) Martin, N. J. A.; List, B. J. Am. Chem. Soc. 2006, 128, 13368-13369.
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30. During our studies, the TFA salt of 9-amino(9-deoxy)epi-quinine was reported to be an excellent catalyst for the asymmetric conjugate addition of carbon-centered nucleophiles to α,β-unsaturated ketones: (a) Xie, J.-W.; Chen, W.; Li, R.; Zeng, M.; Du, W.; Yue, L.; Chen, Y.-C.; Wu, Y.; Zhu, J.; Deng, J.-G. Angew. Chem., Int. Ed. 2007, 46, 389-392.
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32. 3H salt of 9-amino(9-deoxy)epi-quinine was reported, affording moderate to good levels of enantioselectivity (ee's ranging from 47% to 89%). See: (a) Chen, W.; Du, W.; Yue, L.; Li, R.; Wu, Y.; Ding, L.-S.; Chen, Y.-C. Org. Biomol. Chem. 2007, 5, 816-821.
33. Theoretical studies based on DFT calculations to understand the origin of these phenomena (e.g., the absence of a marked matched-mismatched catalyst ion pair combination) are now underway.
34. 2 = c-hexyl, 23% yield, 81% ee after 96 h at 70 °C.