The chemical polymerization of pyrryl Mannich base methiodide salt to porphyrins

Er, Song-Swee (1974) The chemical polymerization of pyrryl Mannich base methiodide salt to porphyrins. Masters thesis, Memorial University of Newfoundland.

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Abstract

Pyrryl Mannich base methiodides were polymerized in both anhydrous hydroxylic and nonhydroxylic solvents with the hope of clarifying some aspects of the mechanism of porphyrin formation. Although a mixture of type isomers were obtained, the product composition was found to consist of ~ 95% type (III and IV) and ~ 5% type (I and II) isomers from various solvents. The results suggested that the isomer composition is not dependent on the presence of “active” hydrogen in the solvent, and polymerization is not due to separation of formaldehyde (or equivalent) from the pyrrole and then a “random” polymerization; formation of type III and IV porphyrins is an inherent property of trimethylaminopyrrole salts and rearrangement in some form is a normal part of polymerization. On the basis of these results and published data, an intermediate with ring D porphobilinogen unit in the pyrrolenine form at right angles to the macrocycle formed from the other three pyrrole units and methane bridges is suggested and a scheme for the natural type III porphyrin formation is also proposed. -- A new compound diethyl 2,5-dimethyl-3,6-pyrazine-dithiolcarboxylate is reported as a by-product of a pyrryl thiolester synthesis.

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