Caffeine (I) and theobromine (II) reacted with pyridine in the presence of hypochlorous acid to give N-(8-xanthinyl)pyridinium salt, which were characterised as the triiodides (IIIa and IIIc) and monoiodides (IIIb and IIId). Treatment of N-(8-caffeinyl)pyridinium iodide (IIIb) with sodium hydroxide afforded sodium 5-(8-caffeinyl)imino-1, 3-pentadien-1-olate (IV). This experiment clarified the mechanism for the color reaction of caffeine by hypochlorous acid-pyridine method.
