Condensation of dipyrromethane with 2-formyl-5-methylpyrrole yields, 1,19-dimethyl-1,19-dideoxybiladiene-ac dihydrobromide, which can be cyclised in the presence of nickel or cobalt ions to give the corresponding metal 1,19-dimethyltetradehydrocorrin salts. Hydrogenation of these salts under a wide variety of experimental conditions gives a mixture of the metal 1,19-dimethyl-corrin and -4,5-dihydrocorrin salts, which have been separated and isolated as the perchlorates. The corrin has also been isolated as the neutral dicyanocobalt(III) complex.
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Johnson et al. (1972) studied this question.