A new short synthesis route for favipiravir and its analogue: Their tautomerization behaviour

Abstract

The study of tautomerism in biologically relevant heterocycles is essential, as it directly affects their chemical properties and biological function. Lactam–lactim tautomerization in pyridine/pyrazine derivatives is such a phenomenon. Favipiravir, a pyrazine derivative, is an essential antiviral drug molecule having notable performance against SARS-CoV-2. Along with a better yielding synthetic method for favipiravir, we have also investigated the lactam–lactim tautomerization of favipiravir and its analogous molecules. Most of these molecules were crystalized and studied for various interactions in their lattice. Many interesting supramolecular interactions such as hydrogen bonding, π–π stacking and halogen bonding were revealed during the analysis. Some of these structures show interesting F–F halogen bonding and water channels in their solid state.