Synthesis of ABC‐Type 22‐Oxacorroles Bearing Three Different Five‐Membered Heterocycles at the meso Positions

Abstract

The acid‐catalyzed [3+2] condensation of appropriate tripyrrane and dipyrromethane yields first examples of two novel ABC type 22‐oxacorroles containing three different types of five‐membered heterocycles such as pyrrole, thiophene, and furan at three meso‐positions in 8–12 % yields. The two 22‐oxacorroles were characterized by HR‐MS, 1D & 2D NMR spectroscopy, absorption, fluorescence, electrochemical and DFT studies. The absorption maxima and quantum yields of the oxacorroles were found to be dependent on the relative positions of meso‐heteroaryl substituents and absorption bands appeared in the region of 410–660 with low quantum yields (0.08–0.14). The electrochemical and DFT studies reveal that the redox properties of 22‐oxacorroles were significantly altered by replacing six‐membered meso‐aryl groups with three different heterocycles. The meso‐heteroaryl substituents such as furyl, pyrrolyl and thienyl groups were aligned with respect to the plane of macrocycles with varying degrees of dihedral angles.