The chemical polymerization of monopyrroles to porphyrins

Wells, Alvin Earl (1969) The chemical polymerization of monopyrroles to porphyrins. Masters thesis, Memorial University of Newfoundland.

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Abstract

The biogenesis of porphyrins and the intermediates in the biogenetic formation of porphyrins are briefly discussed. It is clear that the selective formation of porphyrin type isomers in an enzyme system can not, as yet, be duplicated by the chemical polymerization of monopyrroles. However, it has been shown that the type isomer composition may vary with the condition~ under which the polymerization is done. -- Trimethylaminomethylpyrrole salts were polymerized in an organic solvent in hopes of clarifying some aspects of the mechanism of porphyrin formation. Although a mixture of type isomers was obtained, the results indicated that the cyclization was not completely random. The polymerization appears to involve a number of different reactions in competition with each other. -- The investigation of Raney nickel desulfurization of pyrrole thiolesters was continued and it was found that the thiolester residue can be converted exclusively to a methyl group in very good yield. A brief account of previous results is given. -- When a pyrrole, containing both a thiolester residue and a methyl group, was treated with bromine under anhydrous conditions, it was found that the thiolester, rather than the methyl group, was being attacked. A very limited investigation of this reaction was carried out to determine if it would be a useful route in porphyrin syntheses. -- Some new dipyrromethanes were synthesized and some of the problems encountered in dipyrromethane reactions are discussed.

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