Bromination of 'endo-benzocyclobutanorbornene': Synthesis of 'endo-11,12-dibromobenzocyclobutanorbornene': High-temperature bromination - Part XIV

The electrophilic addition of Br to 'endo-benzocyclobutanorbornene' 5 at -50degrees led in high yield to the formation of the rearranged dibromides 6 and 7. However, high-temperature bromination of 5 in decalin at 150degrees gave exclusively nonrearranged product 8 in 98% yield. From the elimination of nonrearranged product 8, 'endo-bromobenzocyclobutanorbornene' 9 and 'endo-benzocyclobutanorbornene' 5 were obtained. Similarly. bromination of monobromide 9 at 77degrees yielded the nonrearranged tribromide 12 in quantitative yield. The dehydrobromination of 12 provided the 'endo 11,12-dibromobenzocyclobutanorbornene' 3 in high yield, which is a synthon for the trimerization reactions