Bromination of an N-carbethoxy-7-aza-2,3-benzonorbornadiene and synthesis of N-carbethoxy-7-aza-2,3-dibromo-5,6-benzonorbornadiene: high temperature bromination. Part 14

The electrophilic addition of bromine to an N-carbethoxy-7-aza-2,3-benzonorbornadiene at 0°C led in high yield to the formation of rearranged dibromides. However, high-temperature bromination of N-carbethoxy-7-aza-2,3-benzonorbornadiene in carbon tetrachloride at 77°C while irradiating, gave exclusively non-rearranged products. From the elimination of these non-rearranged products, N-carbethoxy-4-bromo-7-aza-2,3-benzonorbornadiene was obtained as the sole product. Similarly, bromination of monobromide N-carbethoxy-4-bromo-7-aza-2,3-benzonorbornadiene at 77°C yielded non-rearranged tribromides. The dehydrobromination of these tribromides provided the N-carbethoxy-5,6-dibromo-7-aza-2,3-benzonorbornadiene in high yield, which is a synthon for trimerization reaction.