Electrophilic substitution in pyrroles. Part 5. Reaction of dipyrrylmethanes with arenediazonium ions

Abstract

Dipyrrylmethanes react with arenediazonium ions in acid solution to form azopyrroles and formaldehyde. At low pH cleavage of the methylene bridge is brought about by attack of hydrogen ions, but at higher pH arenediazonium ions assume this role. In the reaction of benzylpyrrole, benzyl alcohol was detected as a product, suggesting formation of a benzyl carbonium ion. The relevance of these studies to the van den Bergh test for bilirubin is considered.