Suprafacial and antarafacial paths for the thermal vinylcyclopropane-to-cyclopentene rearrangement of 1-ethenylbicyclo[4.1.0]heptane to bicyclo[4.3.0]non-1(9)-ene

The gas phase thermal rearrangement of 1-ethenylbicyclo[4.1.0]heptane at 338 degrees C gives the expected vinylcyclopropane-to-cyclopentene product, bicyclo[4.3.0]non-1(9)-ene. The analogous rearrangement of 1-(2'-(E)-d-ethenyl)bicyclo[4.1.0]heptane takes place with the allylic moiety being utilized in both suprafacial and antarafacial stereochemical ways, for both endo and exo isomers of 8-d-bicyclo-[4.3.0]non-1(9)-ene are formed. The product ratio, defined by deuterium NMR in the presence of Ag(fod) and Yb(fod)(3) shift reagents, corresponds to (79 +/- 2)% suprafacial (sr + si) and (21 +/- 2)% antarafacial (ar + ai) reaction stereochemistry.