Oxidation of 2-methylpyrroles with perchlorinated iron(III) metalloporphyrin catalysts: a versatile synthesis of symmetric and asymmetric dipyrromethanes

A variety of substituted 2-methylpyrroles (3-8) were oxidized using the metalloporphyrin catalysts iron(III) meso-tetra(2, 6-dichloro-3-sulphonatophenyl)-beta-octachloroporphyrin chloride 1 and iron(III) meso-tetra(2,6-dichlorophenyl)-beta-octachloroporphyrin chloride 2 under very mild conditions. Treatment of the resulting allylic alcohols 3a-8a with alpha-free pyrroles 9 and 10 resulted in a very efficient synthesis of the corresponding dipyrromethanes 3b-8b and 3c-8c. Furthermore, the above allylic alcohols when treated with furfurylamine produced the novel (2-furylmethyl)-2-pyrrolylmethylamines 3d-8d.