title: Direct synthesis of palladium porphyrins from acyldipyrromethanes.
abstract: [reaction: see text] Palladium porphyrins are valuable photosensitizers and luminescent agents in biology and materials chemistry. New methodology is described wherein a 1-acyldipyrromethane is converted into the palladium chelate of a trans-A(2)B(2) porphyrin via a one-flask reaction. The reaction entails self-condensation of the 1-acyldipyrromethane in refluxing ethanol containing KOH (5-10 mol equiv) and Pd(CH(3)CN)(2)Cl(2) (0.6 mol equiv) exposed to air. This direct route to palladium porphyrins is more expedient than the four steps of the traditional synthesis: (1) reduction of the 1-acyldipyrromethane; (2) acid-catalyzed condensation; (3) oxidation of the porphyrinogen intermediate; and (4) metal insertion. The new synthesis requires neither acid nor DDQ and formally entails only a 2e(-) + 2H(+) oxidation overall versus the traditional multistep synthesis which requires a 2e(-) + 2H(+) reduction per each 1-acyldipyrromethane (4e(-) + 4H(+) overall) followed by a 6e(-) + 6H(+) oxidation. The analogous reaction of a 1,9-diacyldipyrromethane and a dipyrromethane also gives the palladium porphyrin. Seven palladium porphyrins have been prepared in yields of 25-57%. The direct route also can be used with Cu(OAc)(2).H(2)O to give the copper porphyrin albeit in low yield. In summary, this methodology readily affords palladium porphyrins directly from acyldipyrromethanes.
authors.affiliation: Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, USA.
authors.forename: Duddu S
authors.initials: DS
authors.lastname: Sharada
authors.forename: Ana Z
authors.initials: AZ
authors.lastname: Muresan
authors.forename: Kannan
authors.initials: K
authors.lastname: Muthukumaran
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Lindsey
mesh_terms: D002384:Catalysis; D007202:Indicators and Reagents; D049408:Luminescent Agents / Q000138:chemical synthesis*; D008665:Metalloporphyrins / Q000138:chemical synthesis*; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry*; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010165:Palladium / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry*
chemical_list: D007202:Indicators and Reagents; D049408:Luminescent Agents; D008665:Metalloporphyrins; D011758:Pyrroles; D010165:Palladium; D008697:Methane