Enantioselective Catalysis of the Aza-Cope Rearrangement by a Chiral Supramolecular Assembly

Casey J. Brown, Robert G. Bergman* and Kenneth N. Raymond*
Department of Chemistry, University of California, Berkeley, California 94720-1460, and Division of Chemical Sciences, Lawrence Berkeley National Laboratory, Berkeley, California 94720
J. Am. Chem. Soc., 2009, 131 (48), pp 17530–17531
DOI: 10.1021/ja906386w
Publication Date (Web): November 12, 2009
Copyright © 2009 American Chemical Society

Abstract

Abstract Image

The chiral supramolecular catalyst Ga4L6 [L = 1,5-bis(2,3-dihydroxybenzoylamino)naphthalene] is a molecular tetrahedron that catalyzes the 3-aza-Cope rearrangement of allyl enammonium cations. This catalysis is accomplished by preorganizing the substrate in a reactive conformation within the host. This work demonstrates that through the use of enantiopure assembly, its chiral cavity is capable of catalyzing the 3-aza-Cope rearrangement enantioselectively, with yields of 21−74% and enantiomeric excesses from 6 to 64% at 50 °C. At lower temperatures, the enantioselectivity improved, reaching 78% ee at 5 °C. This is the highest enantioselectivity to date induced by the chiral cavity of a supramolecular assembly.

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History

  • Published In Issue December 09, 2009
  • Article ASAPNovember 12, 2009
  • Received: July 29, 2009

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