992-32-5Relevant academic research and scientific papers
Pinacol-Pinacolone Rearrangements in vic-Dihydroxychlorins and Bacteriochlorins: Effect of Substituents at the Peripheral Positions
Pandey, Ravindra K.,Isaac, Meden,MacDonald, Ian,Medforth, Craig J.,Senge, Mathias O.,Dougherty, Thomas J.,Smith, Kevin M.
, p. 1463 - 1472 (1997)
Upon reaction with osmium tetraoxide a series of porphyrins and chlorins were converted into the corresponding vic-dihydroxychlorins and bacteriochlorins. The presence of an electron-withdrawing substituent at a peripheral position on the porphyrins or chlorins deactivated that particular pyrrole unit toward oxidation, and also directed the oxidation regioselectively to the pyrrole ring opposite to the one bearing the electronegative group. The vic-dihydroxychlorins and bacteriochlorins were converted into the corresponding oxochlorins and dioxobacteriochlorins under pinacol-pinacolone reaction conditions. The migratory behavior of the various substituents were found to be quite complex, since distant conjugated peripheral substituents were able to affect the stability of the carbocation intermediates during the process; the ability to rearrange was affected not only by the intrinsic nature of the migratory group but also by steric and electronic factors operative elsewhere on the porphyrin and chlorin macrocycles. Preferential migration of the propionic ester over the methyl substituent in dioxobacteriochlorins obtained from 2,3,12,13-tetrahydroxycoproporphyrin II tetramethyl ester (IUPAC nomenclature) under pinacol-pinacolone conditions was confirmed by a single crystal X-ray study. The dioxobacteriochlorins obtained from mesoporphyrin III dimethyl ester and coproporphyrin II tetramethyl ester were converted into the corresponding dithio-analogues using Lawesson's reagent; this caused a red shift of 62 nm (compared with the dioxo compounds) affording long wavelength absorption at λmax 746 nm.
Synthesis of a series of mono-meso-arylmesoporphyrins III of biological interest and their biliverdin derivatives
Niemevz, Fernando,Vazquez, Ma. Soledad,Buldain, Graciela Y.
, p. 875 - 882 (2008/09/21)
Synthesis of a series of mono-meso-arylmesoporphyrins III using a MacDonald-type 2+2 condensation is described. In this method, the substituted 1,9-diformyldipyrromethane is treated with a dipyrromethane-1,9-dicarboxylic acid under acidic conditions. The 5-aryldipyrrolic unit was obtained by condensation of tert-butyl, ethyl, or benzyl 4-ethyl-3-methyl-1H-pyrrole-2- carboxylate with different aromatic aldehydes in the presence of 4-toluene-sulfonic acid. In order to obtain the corresponding mesobiliverdins, chemical oxidation of each mesoporphyrin was carried out. Each meso-arylmesoporphyrin rendered two isomeric arylbiliverdins, as the porphyrin meso-aryl bridge is not cleaved. Georg Thieme Verlag Stuttgart.
Syntheses of symmetrically substituted 5-alkyl- and 5-aryl-dihydrodipyrrins and of porphyrins and bisporphyrins therefrom
Lee, David A.,Smith, Kevin M.
, p. 1215 - 1227 (2007/10/03)
Acid-catalysed treatment of 2-unsubstituted pyrroles with alkyl or aryl acetals affords good yields of the corresponding symmetrical 5-substituted dihydrodipyrrins (e.g. 7, 19, 38, 51, 52). Using MacDonald '2 + 2' methodology, such dihydrodipyrrins are transformed in several steps into 5,15-disubstituted porphyrins (e.g. 5, 23, 24, 26, 36), wherein the 5- and 15-substituents can be identical or different. Further functionalization of 5 affords nickel(II) 5-vinyl-15-substituted porphyrin 4 which, after Vilsmeier formylation (POCl3-DMF) of the nickel(II) complex, yields the corresponding nickel(II) 5-(formylvinyl)porphyrin 3; cyclization under acidic conditions then gives the nickel 15-phenylbenzochlorin 1. Nickel(0)-catalysed reductive dimerization of the nickel(II) 15-(p-chloromethylphenyl)porphyrm 48 yields the dihydrostilbene dimer 53, which can also be obtained in lower yield by reductive dimerization of 5-(p-chloromethylphenyl)dihydrodipyrrin 57, followed by MacDonald-type cyclization and metallation of the free-base dimer 54.
