作者:Kenneth B. Wiberg、Dean R. Artis、G. Bonneville
DOI:10.1021/ja00021a024
日期:1991.10
The dehalogenations of 1,5-dihalobicyclo[3.1.0]hexanes and 1,6-dihalobicyclo[4.1.0]heptanes have been studied in solution and in the gas phase. The solution reactions led to the formation of bicyclo[3.1.0]hex-1(5)-ene and bicyclo[4.1.0]hept-1(6)-ene, respectively, but this was followed by rapid ene reactions forming dimers, which then coupled to form tetramers. The cyclopropenes could be trapped as Diels-Alder adducts. In the gas phase, with use of either potassium atoms or solid methyllithium, the products of thermal ring opening, methylenecyclopentene and methylenecyclohexene, were formed. A set of theoretical calculations was carried out dealing with the strain energies, inversion barriers, bond properties, and atom properties of bicyclo[1.1.0]but-1(3)-ene, bicyclo[2.1.0]pent-1(4)-ene, and the cyclopropenes from the experimental study. Whereas bicyclohexene and bicycloheptene appear to be fairly normal compounds except for their high strain energies, bicyclopentene may be a transition state for the carbon scrambling of methylenecyclobutylidene, and bicyclobutene has an unusual structure and charge-density distribution.