Facile Elaboration of Porphyrins via Metal-Mediated Cross-Coupling

Metal-mediated cross-coupling methodologies have been successfully employed to porphyrinic systems, providing a powerful, versatile, and general synthetic approach for the fabrication of elaborated porphyrin structures. A large number of coupling reactions have been carried out at two halogenated porphyrin templates, [2-bromo-5,10,15,20-tetraphenylporphinato]zinc and [5,15-dibromo-10,20-diphenylporphinato]zinc, generating a variety of porphyrins, 10 of which are novel: [2-n-butyl-5,-10,15,20-tetraphenylporphinato]zinc(II), [2-(2,5-dimethoxyphenyl)-5,10,15,20-tetraphenylporphinato]-zmc(II),[2-(9-anthracenyl)-5,10,15,20-tetraphenylporphinato]zinc(II), [2-vinyl-5,10,15,20-tetraphenylporphinato]zinc(II), [2,5,10,15,20-pentaphenylporphinato]zinc(II), [2-isobutyl-5,10,15,20-tetraphenylporphinato]zinc(II), [2-(pentafluorophenyl)-5,10,15,20-tetraphenylporphinato]zinc(II), [5,15-bis-[[2-(4′-methyl-2′-pyridyl)-4-pyridyl]methyl]-10,20-diphenylporphinato]zinc(II), [5,15-divmyl-10,20-diphenylporphinato]zinc(II), [5,15-bis(2,5-dimethoxyphenyl)-10,20-diphenylporphinato]zinc(II), and [5,15-bis(pentafluorophenyl)-10,20-diphenylporphinato]zinc(II). The structures of [2,5,10,15,20-pentaphenylporphinato]zinc(II) and 5,15-bis-(pentafluorophenyl)-10,20-diphenylporphyrin have been determined; X-ray data are as follows: P2₁/n with a = 21.425(4) Å, b = 9.718(1) Å, c = 24.905(2) Å, β = 110.83(1)°, V = 4846(3) ų, d_calc = 1.260 g cm⁻³, and Z = 4 for the former; and P2₁/c with a = 15.223(2) Å, b = 10.162(1) Å, c = 12.375(2) Å, β = 112.75(2)°, V= 1765.6(9) ų, d_calc = 1.495 g cm⁻³, and Z = 2 for thelatter. This study demonstrates that cross-coupling reactions at the porphyrin periphery are seemingly not subject to the steric or electronic constraints that often limit the scope of these reactions in simple aryl and vinyl systems.