Bromination of benzobicyclic system with 1,2-dibromotetracholoroethane: unusual radical rearrangement

The bromination reaction of a benzobicyclic system with 1,2-dibromotetracholoroethane (DBTCE) was studied. For tricyclo[6.2.2.02,7]dodeca-2,4,6,9,11-pentaene, rearranged and non-rearranged products were obtained. Bromination of 11-oxatricyclo[6.2.1.02,7]undeca-2,4,6,9-tetraene with DBTCE gave non-rearranged products whereas brominations of (1R(S),8R(S))-9-bromotricyclo[6.2.2.02,7]dodeca-2,4,6,9,11-pentaene and (1S(R),8S(R))-9,10,11-tribromotricyclo[6.2.2.02,7]dodeca-2,4,6,9,11-pentaene with DBTCE gave only rearranged products. In addition, the reaction of (1S(R),8S(R))tricyclo[6.3.1.02,7]dodeca-2,4,6,9-tetraene with the same reagent resulted in the formation of allylic bromination products. The radicalic reaction mechanism is discussed. All compounds are characterized properly, in particular by NMR spectra and by chemical transformation.