One-pot formation of six bonds: pseudo-six-component diastereoselective synthesis of pyridinium-containing piperidin-2-ones

The present study describes a multicomponent synthesis of pyridinium derivatives of piperidin-2-ones from aromatic aldehydes, malononitriles, pyridines, haloacetates, and ammonium acetate. The synthesis occurs through the in situ formation of pyridinium ylide and involves the Knoevenagel—Michael—Mannich cyclization cascade. 1-[(3RS,4SR,6RS)-4,6-Diaryl-5,5-dicyano-2-oxopiperidin-3-yl]pyridin-1-ium halides with three stereocenters and 1-[(3RS,4SR,5SR,6RS)-5-alkoxycarbonyl-4,6-diaryl-5-cyano-2-oxopiperidin-3-yl]pyridin-1-ium halides with four stereocenters were synthesized.