5,10,20,25,35,40-Hexanornonapyrrin: The Largest Structurally Characterized Oligopyrrole Prepared to Date

The synthesis and X-ray diffraction-based characterization of a nonapyrrolic oligomer 2 [5,5‘‘-bis((2-(ethoxycarbonyl)-3,4,3‘,4‘,3‘‘,4‘‘-hexamethyl-5,2‘:5‘,2‘‘-terpyrrol-5‘‘-yl)vinyl)-3,4,3‘,4‘,3‘‘,4‘‘-hexamethyl-2,2‘:5‘,2‘‘-terpyrrole] is reported. It was prepared by condensing 2 equiv of the 2-(ethoxycarbonyl)-2‘‘-formyl-3,4,3‘,4‘,3‘‘,4‘‘-hexamethyl-5,2‘:5‘,5‘‘-terpyrrole (8) with 1 equiv of 3,4,3‘,4‘,3‘‘,4‘‘-hexamethyl-2,2‘:5‘,2‘‘-terpyrrole (9). A similar procedure, involving the condensation of 1 equiv of the 2-(ethoxycarbonyl)-2‘‘-formyl-3,4,3‘,4‘,3‘‘,4‘‘-hexamethyl-5,2‘:5‘,5‘‘-terpyrrole (8) with 1 equiv of 2-(ethoxycarbonyl)-3,4,3‘,4‘,3‘‘,4‘‘-hexamethyl-5,2‘:5‘,2‘‘-terpyrrole (10) was found to give rise to the corresponding hexameric system 4 bis(2-(ethoxycarbonyl)-3,4,3‘,4‘,3‘‘,4‘‘-hexamethyl-5,2‘:5‘,2‘‘-terpyrrol-5‘‘-yl)methene, a system that was likewise characterized by X-ray diffraction methods. It was also found that replacing the monoformyl terpyrrole 8 by the corresponding bipyrrole, namel...