Synthesis and chemistry of new benzoporphyrins

Benzoporphyrins 5 and 6 are the major products obtained from the cycloaddit ion reactions of beta-fused metallopyrroloporphyrins 1. and 2 with dimethyl acetylenedicarboxylate. In the presence of excess dienophile a bis-adduct is also obtained which undergoes retro-Diels-Alder reaction to produce 5. B enzoporphyrin 5 was converted into the first reported beta-fused benzochlor ins 9-11, and the free-base benzoporphyrin 12 was regioselectively brominat ed to afford 13. Exhaustive bromination also yields hexabromobenzoporphyrin 14. (C) 1999 Elsevier Science Ltd. All rights reserved.