A palladium-catalyzed intramolecular Heck/Hydrogenation approach towards the synthesis of praziquantel

Abstract Starting from 3-methoxy N -acylpyrazinium salts, a new approach towards the synthesis of the antischistosomal drug praziquantel (PZQ) has been developed. Utilization of a palladium-catalyzed intramolecular Heck reaction to form dehydro-PZQ followed by a Hydrogenation step, in a stepwise or one-pot manner, allowed for the gram scale synthesis of PZQ in 4 or 5 steps and in good overall yields. This methodology proved to be well suited for generating the pyrazino[1,2-a] isoindole and pyrazino[1,2-a] benzazepine analogues of PZQ.