Generation and stereocontrolled trapping of 3-phenylcyclopropene and its derivatives

Selective methods for the preparation of 3-phenylcyclopropene and its 1-substituted derivatives are provided. The parent cyclopropene is readily trapped in (3+2)- and (4+2)-cycloadditions that lead to exo-3-phenyl-1,2-disubstituted cyclopropanes. Ab initio calculations suggest that the lowest energy conformation has the plane of the benzene ring perpendicular to the cyclopropene π-bond but with a low rotation barrier.