CYCLOALLENES .8. 1,2,4-CYCLOHEXATRIENE, AN ISOBENZENE, AND BICYCLO[4.4.0]DECA-1,3,5,7,8-PENTAENE, AN ISONAPHTHALENE - GENERATION AND TRAPPING REACTIONS

The addition of bromofluorocarbene to cyclopentadiene and indene yields stable geminal endo‐fluoro, exo‐bromocyclopropane derivatives, which when treated with methyllithium lead to isobenzene 1 and isonaphthalene 2, respectively. These cycloallenes can be trapped in cycloaddition reactions, for example with styrene. This reaction sequence can be converted into a one‐pot procedure if dibromocarbene is generated at low temperatures from tetrabromomethane and methyllithium and treated in situ for the subsequent reactions.—Because the synthesis of a new isomer of benzene is not reported every day, the experimental study immediately precedes this profile of isobenzene 1 obtained from quantum chemical calculations. These results include data regarding its heart of formation, equilibrium geometry, racemization, diradical character, IR spectrum, and chemoselectivity in its [2 + 2] cycloaddition reaction with styrene. (Figure Presented.) Copyright © 1992 by VCH Verlagsgesellschaft mbH, Germany