J. A. Duncan, R. Hendricks, Katy S. Kwong
Nov 1, 1990
Citations
0
Influential Citations
12
Citations
Journal
Journal of the American Chemical Society
Abstract
The synthesis and separate thermal rearrangements of (±)-(1R*,4S*,7S*)-7-[(R*)-1,2-butadienyl]-1-methyl-bicyclo[2.2.1]hept-2-ene (8a) and (±)-(1R*,4S*,7S*)-7-[(S*)-1,2-butadienyl]-1-methylbicyclo[2.2.1]hept-2-ene (8b) are described. Both 8a and 8b are shown to rearrange to (±)-cis-1-ethylidene-3a,4,5,7a-tetrahydro-6-methylindene (9) and (±)-cis-1-ethylindene-3a,4,5,7a-tetrahydro-3a-methylindene (10) with greater than 90% stereoselectivity. Epimer 8a gives predominantly (E)-9 and (Z)-10, whereas 8b gives predominantly (Z)-9 and (E)-10, results consistent with either a six-electron [σ2s+π2s+π2s] Cope or eight-electron [σ2s+π2s+(π2s+π2a)] augmented Cope process. Stereochemical assignments (8a vs 8b, (E)-9vs (Z)-9, and (E)-10 vs (Z)-10) are based upon experiments in nuclear Overhauser effect (NOE) difference spectroscopy