Syntheses of type-I porphyrins via monopyrrole tetramerization

Article abstract of DOI:10.1016/0040-4039(96)01632-2

Treatment of 2-[(N,N-dialkylamino)methyl]pyrrole-5-carboxylic acids (e.g. 10,12 or 11,13) in methanol with K₃Fe(CN)₆ gives type-I porphyrins (etioporphyrin-I 7, coproporphyrin-I tetramethyl ester 16, respectively); with pyrroles 10,12 the product 7 is contaminated with about 8% of other type-isomer(s).