1,3-Bridged Cyclopropenes

Article abstract of DOI:10.1021/ja00021a025

Solid fluoride deposited on glass helices has been used to effect the gas-phase elimination of 1-(trimethylsilyl)-7-chlorobicyclo[4.1.0]heptane and 1-(trimethylsilyl)-8-chlorobicyclo[5.1.0]octane to yield bicyclo[4.1.0]hept-1(7)-ene and bicyclo[5.1.0]oct-1(8)-ene, respectively. Bicyclo[4.1.0]hept-1(7)-ene dimerizes below ca. -90 °C via an ene reaction to yield a new cyclopropene, which then couples to form tetramers. The structures of two tricyclohexane tetramers were determined by X-ray crystallography. The ene dimer was found to react with molecular oxygen to yield two carbonyl compounds identified as 2-(1-bicyclo[4.1.0]heptyl)cyclohexene-1-carboxaldehyde and 3-(1-bicyclo[4.1.0]heptyl)cyclohept-2-en-1-one. These compounds are thought to result from the reaction of molecular oxygen with carbenes that would arise from cyclopropene - vinylcarbene rearrangements. Bicyclo[5.1.0]oct-1(8)-ene is considerably more stable than its lower homologue but also dimerizes via an ene reaction 7-Chlorobicyclo[4.1.0]hept-1(7)-ene rearranges below -90 °C to yield 2-chloro-1,3-cycloheptadiene.