PIFA-promoted intramolecular oxidative cyclization of pyrrolo- and indolo[1,2-a]quinoxalino-appended porphyrins: an efficient synthesis of meso,β-pyrrolo- and indolo[1,2-a]quinoxalino-fused porphyrins

Abstract

We have developed an efficient protocol for the synthesis of meso,β-pyrrolo- and indolo[1,2-a]quinoxalino-fused porphyrin systems 7–9 by PIFA-promoted intramolecular oxidative cyclization of easily accessible meso-pyrrolo- and indolo[1,2-a]quinoxalino-appended porphyrins 6a–j. The absorption spectra of meso,β-pyrrolo- and indolo[1,2-a]quinoxalino-fused porphyrins 7–9 displayed bathochromic shifted (100–150 nm) and broadened Soret bands and Q bands in addition to intense band near IR region. The indolo[1,2-a]quinoxalino-fused porphyrin 9bZn with lower fluorescence quantum yield (0.003) and reduced energy gap (∼1.3 eV) was found to sensitize singlet oxygen effectively.