HIGHLY VERSATILE METHODS FOR THE SYNTHESIS OF QUINONYLPORPHYRINS VIA BENZANNULATION OF FISCHER CARBENE COMPLEXES AND PALLADIUM-CATALYZED CROSS-COUPLING REACTIONS

Covalently-Linked porphyrin mono- and tetraquinones with well-defined distances and orientations were synthesized on the basis of two synthetic approaches. (1) The benzannulation of Fischer carbene complexes with meso-(alkynylphenyl)-substituted porphyrins, followed by oxidation, produced quinone-linked porphyrins, with both electron-donating and -withdrawing substituents on the quinone moieties. (2) The palladium-catalyzed Suzuki cross-coupling reactions of (2,5-dimethoxyphenyl)boronic acid with porphyrin meso-aryl triflates and aryl bromides, followed by subsequent demethylation and oxidation, gave meso-(benzoquinonylphenyl)-substituted porphyrins.