First synthesis of meso-substituted pyrrolo[1,2-a]quinoxalinoporphyrins.

A synthetic protocol for the construction of new meso-substituted pyrrolo[1,2-a]quinoxalinoporphyrins is described starting from 5-(4-amino-3-nitrophenyl)-10,15,20-triphenylporphyrin. The reaction of this porphyrin with 2,5-dimethoxytetrahydrofuran, followed by the reduction of the nitro group in the presence of NiCl2/NaBH4 afforded 5-(3-amino-4-(pyrrol-1-yl)phenyl)-10,15,20-triphenylporphyrin. This triphenylporphyrin underwent a Pictet-Spengler cyclization after the reaction with various aromatic aldehydes followed by in situ KMnO4 oxidation to form target porphyrin analogues in good yields. The structures of all synthesized products were established on the basis of spectral data and elemental analyses.