Combined computational and experimental studies of the mechanism and scope of the retro-Nazarov reaction.
Density functional theory calculations (B3LYP/6-31+G) demonstrate that conjugating and electron-donating substituents at carbons three and four of a cyclopentenyl oxyallylic cation should have a rate-accelerating effect on the retro-Nazarov reactions of these species. The retro-Nazarov reaction of these intermediates is predicted to exhibit significant torquoselectivity when carbon three is substituted with a methoxy and a methyl group. Experimental studies show that oxyallylic cations can undergo effective retro-Nazarov reactions when two alkyl and one aryl/vinyl groups are on carbons three and four. An equal number of alkyl substituents or a single aryl substituent is not effective in promoting the reaction. Interestingly, a single alkoxy substituent at carbon three is sufficient for the retro-Nazarov reaction to occur. The methodology developed was used in a total synthesis of the natural product turmerone.
Harmata
Michael
M
Contribution from the Department of Chemistry, University of Missouri-Columbia, Columbia, MO 65211, USA. harmatam@missouri.edu
Schreiner
Peter R
PR
Lee
Dong Reyoul
DR
Kirchhoefer
Patrick L
PL