Cascade reaction synthesis of multisubstituted bicyclic pyridone derivatives

Synthesis of 3‐Aminopyrido[2,1‐a]isoquinolin‐4‐one Derivatives via Condensation of Azlactones with 1‐Alkyl‐3,4‐dihydroisoquinolines

“…The proposed mechanism for the formation of 4 H ‐pyrido[2,1‐ a ]isoquinolin‐4‐one 25 a is described in Scheme 1. The Michael addition [28a–e] of the enamine form of isoquinoline 18 a to azlactone 5 , followed by the elimination of alcohol and imine‐enamine tautomerization leads to the formation of a isomeric mixture E,E ‐23 a and E,Z ‐23 a . Heating this mixture in DMF leads to isomerization of compound E,E ‐23 a to E,Z ‐23 a , which is capable of closing the pyridine cycle as a result of the attack of azlactone by the nitrogen atom of the isoquinoline ring.…”

Heterocyclic Ketene Aminals

“…13 The reaction proceeds via Michael addition, intramolecular cyclization and ring cleavage and enol-keto tautomerism.…”

Base Induced Condensation of Malononitrile with Erlenmeyer Azlactones: An Unexpected Synthesis of Multi‐Substituted Δ2‐Pyrrolines and Their Cytotoxicity

“…One of the most important reactions is conversion of glycine into different amino acids via azlactone intermediate . Some other important reactions are aza‐ene reaction with enamines, lactone ring oxygen replacement from other hetero atoms like N ‐ or S ‐containing substrates, incorporation of allyl functionality in a selective manner to the Erlenmeyer azlactones core structure . Alkylidene azlactones have been used in asymmetric hetero‐Diels‐Alder reactions, undergo reaction with isatins and vinyl cyclopropanes, which process through [4+2] annulations and [3+2]‐cycloaddition, respectively.…”