1 (E)-Deuteriobutadiene and cyclopropene react at 0" C to give 2-endo-deuteriobicyclo [4. l. 0] hept-3-ene; 1-(2)-deuteriobutadiene leads to the 2-em-deuterio bicyclic product. Analysis of these products through 2H NMR spectroscopy reveals complete stereospecificity, indicating that the transition structure having an endo orientation of diene and cyclopropene is strongly favored over the alternative exo geometry.
