Simple Methodology for Syntheses of Porphyrins Possessing Multiple Peripheral Substituents with an Element of Symmetry

New methodology was developed for synthesis of regiochemically pure porphyrins with D 2 h symmetry (e.g. 9 ) via tetramerization reactions involving two different pyrroles. The two pyrrole components were a 2,5-diunsubstituted pyrrole (e.g. 11 ) and a 2,5-bis[( N,N- dimethylamino)methyl]pyrrole (e.g. 10 ), the latter being formed from a 2,5-di-unsubstituted pyrrole by treatment with excess Eschenmoser's reagent ( N,N- dimethylmethyleneammonium iodide). A bis-butanoporphyrin 16 was transformed into the corresponding opp -bis-benzoporphyrin 17 by treatment with DDQ. The synthetic method was further extended to allow the synthesis of more unsymmetrical porphyrins, with C 2 v symmetry (e.g. 32 ), by reacting a tripyrrane (e.g. 27 ) with a 2,5-bis[( N,N- dimethylamino)methyl]pyrrole (e.g. 18 ). The structures and substituent arrays in both type of porphyrins were confirmed by single-crystal X-ray crystallography.