Optimizing the synthesis of 5,10-disubstituted tripyrromethanes

Condensation of aldehydes with pyrrole in the presence of acid catalyst gave the mixture of dipyrromethanes and tripyrromethanes. The major product was switched from dipyrromethanes to tripyrromethanes according to the sequence of adding the reactants and catalyst. Higher oligomers such as tetrapyrromethane and pentapyrromethane were isolated and characterized from the reaction of 4-methoxycarbonylbenzaldehyde with pyrrole.