S. Ito et al., A new synthesis of benzoporphyrins using 4,7-dihydro-4,7-ethano-2H-isoindole as an isoindole equivalent, HETEROCYCLE, 52(1), 2000, pp. 399-411
Various benzoporphyrins and their metal complexes were obtained in 100% yie
ld by heating porphyrins fused with bicyclo[2.2.2]octadiene at 200 degrees
C. This thermal (retro Diels-Alder) reaction proceeds very cleanly to give
pure benzoporphyrins without further purification.