Synthesis of extended porphyrins by connection of meso-aryl groups with β-pyrrolic positions

This review focuses on synthetic strategies leading to extended porphyrins, but is limited to examples in which at least one beta-pyrrolic carbon is linked to a meso-aryl substituent. Friedel-Crafts reactions are covered first because historically they were the first reactions employed to link beta-pyrrolic carbons with meso-aryl groups, thus creating new six-membered fused rings. Other reactions inserting heteroatoms follow. Direct cyclizations between an ortho-carbon and a beta-pyrrolic position are presented next. Finally, new highly extended chromophores are described. These compounds are generally obtained in two consecutive reactions. First a Suzuki coupling is used to introduce an aryl group in one or two meso positions. Then the new fused rings are generated by oxidative cyclizations.