Thermal rearrangement of nickel 1,19-disubstituted tetradehydrocorrin salts to nickel porphins

Abstract

Thermolysis of nickel 19-alky-1-methyltetradehydrocorrin perchlorates yields mainly meso-alkylporphins by ring expansin and migration of the alkyl group. In the reaction, the carbon of the original 1-methyl substituent becomes the meso-carbon of the porphin. Similar thermolyses of all but one of the other nickel 1,19-disubstituted tetradehydrocorrin salts examined so far yield the meso-unsubstituted porphins with elimination of the 19-alkyl subsituent. The exception to the generalisation is nickel decamethyltetradehydrocorrin chloride which, after being heated, gave an appreciable amount of the oxide of the meso-methyl porphin together with the meso-unsubstituted porphin as the main product.