title: An efficient synthesis of porphyrins with different meso substituents that avoids scrambling in aqueous media.
abstract: We have developed new conditions that afford regioisomerically pure trans-A2B2-, A3B-, and trans-AB2C-porphyrins bearing aryl and arylethynyl substituents. The porphyrins were prepared by the acid-catalyzed condensation of dipyrromethanes with aldehydes followed by oxidation with p-chloranil or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). Optimal conditions for the condensation were identified after examining various reaction parameters such as solvent composition, acid concentration, and reaction time. The conditions identified (for aromatic aldehydes: EtOH/H2O 4:1, [DPM] = 4 mM, [aldehyde] = 4 mM, [HCl] = 38 mM, 16 h; for arylethynyl aldehydes: THF/H2O 2:1, [DPM] = 13 mM, [aldehyde] = 13 mM, [HCl] = 150 mM, 3 h) resulted in the formation of porphyrins in yields of 9-38% without detectable scrambling. This synthesis is compatible with diverse functionalities such as ester or nitrile. In total, 20 new trans-A2B2-, A3B-, and trans-AB2C-porphyrins were prepared. The scope and limitations of the two sets of reaction conditions have been explored. The methodological advantage of this approach is its straightforward access to building blocks and the formation of the porphyrin core in higher yields than by any other methodology and by using environmentally benign and nonhazardous chemicals.
authors.affiliation: Institute of Organic Chemistry of the Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland).
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Nowak-Król
authors.forename: Rémi
authors.initials: R
authors.lastname: Plamont
authors.forename: Gabriel
authors.initials: G
authors.lastname: Canard
authors.forename: Judicaelle Andeme
authors.initials: JA
authors.lastname: Edzang
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Gryko
authors.forename: Teodor Silviu
authors.initials: TS
authors.lastname: Balaban
mesh_terms: D000447:Aldehydes / Q000737:chemistry; D016227:Benzoquinones / Q000737:chemistry; D055772:Green Chemistry Technology; D010084:Oxidation-Reduction; D011166:Porphyrins / Q000138:chemical synthesis* / Q000737:chemistry; D011758:Pyrroles / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D000447:Aldehydes; D016227:Benzoquinones; D011166:Porphyrins; D011758:Pyrroles; C512015:dipyrromethane; D014867:Water; C000928:dichlorodicyanobenzoquinone
keywords: conjugation; green chemistry; porphyrinoids; synthetic methods