Enantioselective catalysis of the aza-Cope rearrangement by a chiral supramolecular assembly.
The chiral supramolecular catalyst Ga(4)L(6) [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 degrees C. At lower temperatures, the enantioselectivity improved, reaching 78% ee at 5 degrees C. This is the highest enantioselectivity to date induced by the chiral cavity of a supramolecular assembly.
Brown
Casey J
CJ
Department of Chemistry, University of California, Berkeley, California 94720-1460, USA.
Bergman
Robert G
RG
Raymond
Kenneth N
KN