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

The bromination reaction of a benzobicyclic system with 1,2-dibromotetracho loroethane (DBTCE) was studied. For tricyclo[6.2.2.0(2,7)]dodeca-2,4,6,9,11 -pentaene, rearranged and non-rearranged products were obtained. Brominatio n of 11-oxatricyclo[6.2.1.0(2,7)]- undeca-2,4,6,9-tetraene with DBTCE gave non-rearranged products whereas brominations of (1R(S),8R(S))-9-bromotricyc lo[6.2.2.0(2,7)]- dodeca-2,4,6,9,11-pentaene and (1S(R),8S(R))-9,10,11-trib romotricyclo[6.2.2.0(2,7)]dodeca-2,4,6,9,11-pentaene with DBTCE gave only r earranged products. In addition, the reaction of (IS(R),8S(R))tricyclo[6.3. 1.0(2,7)]dodeca-2,4,6,9-tetraene with the same reagent resulted in the form ation of allylic bromination products. The radicalic reaction mechanism is discussed. All compounds are characterized properly, in particular by NMR s pectra and by chemical transformation. (C) 2001 Elsevier Science Ltd. All r ights reserved.