Formation of nickel tetradehydrocorrin derivatives and the reduction of nickel 1,19-dimethyltetrahydrocorrin salts

Abstract

Cyclisation of 1,19-dideoxybiladienes-ac containing one α-methyl substituent and one α-hydrogen may lead either to porphins by heating, or to nickel 1-methyltetradehydrocorrins by cyclisation of basic solutions in presence of nickel ions. Cyclisation of 1,19-dimethyl-1,19-dideoxybilenes-b to nickel 1,19-dimethyltetradehydrocorrin salts is achieved using the same experimental conditions as are required for cyclisation of the corresponding 1,19-dimethyl-1,19-dideoxybiladiene-ac salts. Nickel 1,19-dimethyltetradehydrocorrin salts can be hydrogenated in presence of Raney nickel to the nickel AD-bisdehydrocorrin salts. In the absence of C-2 and C-18 methyl substituents, vigorous hydrogenation of the nickel 1,19-dimethyltetradehydrocorrin salts yields amorphous nickel 1,19-dimethylcorrin salts. Dehydrogenation of the nickel corrin salts gives the crystalline nickel BC-bisdehydrocorrin salts, together with a neutral nickel 5-keto-macrocycle containing seven double bonds. Methylation of the anion derived from a nickel AD-bisdehydrocorrin salt yields a derivative of the corresponding nickel ACD-tridehydrocorrin containing an additional methyl group at C-7.