The electrophilic addition of bromine to an N-carbethoxy-7-aza-2,3-benzonorbomadiene at 0degreesC led in high yield to the formation of rearranged dibromides. However, high-temperature bromination of N-carbethoxy-7-aza-2,3-benzonorbomadiene in carbon tetrachloride at 77degreesC while irradiating, gave exclusively non-rearranged products. From the elimination of these non-rearranged products, N-carbethoxy4-bromo-7-aza-2,3-benzonorbomadiene was obtained as the sole product. Similarly, bromination of monobromide N-carbethoxy-4-bromo7-aza-2,3-benzonorbomadiene at 77degreesC yielded non-rearranged tribromides. The dehydrobromination of these tribromides provided the N-carbethoxy-5,6-dibromo-7-aza-2,3-benzonorbomadiene in high yield, which is a synthon for trimerization reaction. (C) 2002 Elsevier Science Ltd. All rights reserved.