On the Alternative Protonation of Heterocyclic Michler´s Ketone Analogues

ABSTRACT

Heterocyclic analogues of Michler´s ketone, in which its benzene moieties are replaced by two thiophene or thiazole moieties, exhibit certain properties that differ from the ones of the parent aromatic ketone. Thus, the thienylketones are transferred by protonation into intense‐colored proton adducts with polymethinic structure, which differ significantly from the corresponding proton adduct of Michler´s ketone or of ketones containing thiazole moieties in their molecular framework. NMR spectroscopic measurements and quantum chemical calculations explain the spectroscopic behavior of these heteroaromatic ketones.