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Copper-Mediated Nazarov Cyclization/1,2-Sigmatropic Rearrangement
J. Huang, A. J. Frontier*
University of Rochester, USA
23 August 2007 (online)
A stereoselective copper-mediated Nazarov cyclization/Wagner-Meerwein rearrangement produces two types of five-membered spirocyclic products depending on the substrate. Substrates containing a cinnamyl substituent lead to products where the substituent migrates after the Nazarov cyclization, whereas substrates with an alkyl substituent undergo hydrogen migration after cyclization. Six-membered spirocycles can also be formed from the corresponding seven-membered-ring starting material. The enantioselectivities for the reaction are low, but unoptimized.