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

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 meso-fabrications are the first example for porphyrinoid substrates.