Synthesis and chemistry of tricyclic cyclopropene-tricyclo[3.2.2.02,4]nona-2(4),6-diene

The 1,2-bridged tricyclic cyclopropene, tricyclo[3.2.2.02,4]nona-2(4),6-diene (), has been synthesized by the elimination of 2-bromo-4-chlorotricyclo[3.2.2.02,4]-non-6-ene (). Cyclopropene will undergo different isomerizations in ether solution and in neat conditions. Compound rearranged to an anti-Bredt compound via diradical mechanism in ether and tricyclic compound via vinyl carbene mechanism in neat conditions. Compound can be trapped with DPIBF at different temperatures yielding different results: the exo–endo adduct (exo-addition from the view of the cyclopropene and endo-addition from the view of bicyclo[2.2.2]octene) is a sole product at 0°C by slowly addition of methyllithium, and the exo–endo adduct , endo–endo adduct , anti-Bredt adduct , and styrene are isolated at ether refluxing temperature. Styrene is proposed to be formed from endo–endo adduct by diradical mechanism. The chemistry of exo–endo adduct and endo–endo adduct is as well studied. The exo–endo adduct undergoes hydration in trifluoroacetic acid to generate 1,3-cis-diol followed by eliminations of water and formaldehyde to give naphthalene . The endo–endo adduct reacts with water in tetrahydrofuran-containing silica gel to yield 1,4-cis-diol . Both and react with trifluoroacetic acid to form trans-3-hydroxy trifluoroacetate . Compound will undergo hydrolysis and isomerization to generate 1,3-cis-diol in trifluoroacetic acid.