Synthesis, structures, and properties of BCOD-fused porphyrins and benzoporphyrins

Abstract

Bicyclo[2.2.2]octadiene (BCOD)-fused porphyrins with no other substituents were prepared by [2 + 2] and [3 + 1] porphyrin syntheses from ethanodihydroisoindole derivatives in fairly good yields. Thermal retro-Diels-Alder reactions of BCOD-fused porphyrins gave the corresponding benzoporphyrins with no substituent in quantitative yields. Their UV-vis spectra and crystal structures were carefully examined in terms of π-system expansion of the porphyrin ring current. In the cases of monobenzo- and adj-dibenzo-porphyrins, a single Soret band in their UV-vis spectra and no bond alteration in the benzene rings of their crystal structures were observed, while the split Soret bands and the obvious bond alteration in their benzene rings were recorded in the case of opp-dibenzoporphyrin.