Synthesis of a Porphyrin with Fused Five- and Seven-membered Exocyclic Rings from a Cross-conjugated Tetracyclic Dipyrrole

Abstract

1-Aza-7-pyrrolylmethyl-1,4,5,6-tetrahydroazulene 1 was cyclized with 3.5% HBr-AcOH to give a cross-conjugated dipyrrole 3 in good yield; hydrogenation of the double bond gave the tetracyclic dipyrrole 5 and subsequent hydrogenolysis of the benzyl esters, followed by acid catalyzed condensation with diformyldipyrrylmethane 7 gave a porphyrin 8 bearing two fused exocyclic rings.