Porphotetramethenes with 1,3-alternate conformation of pyrrole rings from oxidative N-alkylation of porphyrin tetraphenols

Tetrapyrrole macrocycles, of which the pyrroles are connected by sp2 centers, were readily obtained from porphyrin tetraphenols by air oxidation under basic conditions, followed by N-alkylation. The degree of N-alkylation could be controlled and either di- or tetraalkylated derivatives are obtained in high yields.