B^III–Subporphyrins Bearing Distorted Metal-Coordinating Straps: Cu^II-Assisted meso-Fabrications

Abstract

B III -subporphyrins 4, 5, and 6 possessing metal-coordinating carbaporphyrin-like pockets were synthesized by Suzuki−Miyaura coupling reactions. Compounds 4 and 5 gave Pd II complexes 4-Pd and 5-Pd upon metalation with Pd(OAc) 2 but did not give either their Ni II or Cu II complexes. Conversely, 6 was expected to induce distorted square planar coordination because of its 2,5-di(pyrid-2-yl)pyrrole strap. Indeed reaction of 6 with Cu(OAc) 2 did not give its Cu II complex but produced meso-alkoxy and meso-phenoxy products in the presence of alcohols and phenol, possibly via Cu II -mediated C−H bond functionalization, which was further extended to meso-C−C bond-forming fabrications by using organoboronic acids. These Cu II -mediated C−H bond mesofabrications are the first example for porphyrinoid substrates.