Novel Porphyrinoids from α,α-Linked Oligopyrroles

Abstract

α,α-linked oligopyrroles play a crucial role in the synthesis of expanded porphyrins. The preparation of macrocycles such as porphycenes, amethyrins or cyclopyrroles is based on the coupling or condensation of the proper functionalized bipyrrole or terpyrrole. Although longer α,α-linked oligopyrroles have been reported, their chemical instability has hampered their use as synthetic building blocks. Our group have developed a new family of 2,2’-bipyrroles 1 which possesses a remarkable chemical stability ascribed to the presence of two electron withdrawing groups. Bipyrroles 1 can be easily brominated at the α positions allowing their homologation with pyrrole units by means of palladium catalyzed reactions. This strategy has allowed the concise preparation of quaterpyrrole 2 and sexipyrrole 3. In this presentation, the preparation of these oligomers and their use to synthetize new expanded porphyrins will be discussed. Figure 1