title: Brønsted acid-mediated cyclization-dehydrosulfonylation/reduction sequences: An easy access to pyrazinoisoquinolines and pyridopyrazines.
abstract: An efficient and alternative synthetic approach has been developed to prepare variousN-(arylethyl)piperazine-2,6-diones from 4-benzenesulfonyliminodiacetic acid and primary amines using carbonyldiimidazole in the presence of a catalytic amount of DMAP at ambient temperature. Piperazine-2,6-diones are successfully transformed to pharmaceutically useful pyridopyrazines or pyrazinoisoquinolines and ene-diamides via an imide carbonyl group activation strategy using a Brønsted acid. Subsequent dehydrosulfonylation reactions of the ene-diamides, in a one pot manner, smoothly transformed them to substituted pyrazinones. A concise synthesis of praziquantel (1) has also been achieved through this method.
authors.affiliation: Department of Chemistry, Pondicherry University, Puducherry - 605 014, India.
authors.forename: Ramana Sreenivasa
authors.initials: RS
authors.lastname: Rao
authors.affiliation: Department of Chemistry, Pondicherry University, Puducherry - 605 014, India.
authors.forename: Chinnasamy Ramaraj
authors.initials: CR
authors.lastname: Ramanathan
keywords: Brønsted acid; piperazine-2,6-diones; praziquantel; pyrazinoisoquinoline; pyridopyrazine