Brønsted acid-mediated cyclization–dehydrosulfonylation/reduction sequences: An easy access to pyrazinoisoquinolines and pyridopyrazines

• Ramana Sreenivasa Rao and
• Chinnasamy Ramaraj Ramanathan

Beilstein J. Org. Chem. 2017, 13, 428–440, doi:10.3762/bjoc.13.46

• Ramana Sreenivasa Rao Chinnasamy Ramaraj Ramanathan Department of Chemistry, Pondicherry University, Puducherry – 605 014, India 10.3762/bjoc.13.46 Abstract An efficient and alternative synthetic approach has been developed to prepare various N-(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. Keywords: Brønsted acid; piperazine-2,6-diones