SYNTHESIS AND INTRAMOLECULAR HYDROGEN-BONDING OF SYMMETRICAL DIPYRRYLMETHANES

The title compounds were prepared by converting ethyl 5-methylpyrrore-2-carboxylates into corresponding 5-methyl substituted pyrroles oxydized by surfuryl chloride, bromine, or lead tetraacetate, and then self-condensed without separation and purification, The H-1 NMR analysis and molecular conformation computation revealed that strong intramolecular hydrogen bondings exist in dipyrrylmethane 4(b) and 4(e)(3,3' substituents are formate and acetate esters), while very weak or no intramolecular hydrogen bonding exists in other dipyrrylmethanes.