A new and convenient synthesis of substituted benzobarrelenes

Bromination of 3-bromo-6,7-benzobicyclo [3.2.1] octa-2,6-diene at ?50°C gave anti-tribromo adduct (5) in essentially quantitative yield. The double dehydrobromination of (5) was achieved using potassium tert.- butoxide to give 2-bromo-benzobarrelene (7). Reaction of (7) with n-BuLi and subsequent quenching with CH₃I, CO₂, and dimethylformamide afforded the corresponding substituted benzobarrelenes in high yield.