Facile Synthesis of 4-Oxo-4H-quinolizine-2-carboxamide Derivatives

A facile synthetic method for the construction of 2-substituted-4-oxo-4H-quinolizine based core structure has been successfully developed. The synthesis made use of a one pot Stobbe condensation followed by cyclisation starting from the commercially available 2-pyridinecarbaldehyde. The structure of the formed 4-oxo-4H-quinolizine-2-carboxylate was fully confirmed by MS, 1H NMR, 13C NMR, COSY, HMBC and HSQC spectra. The ethyl carboxylate moiety was then further functionalized via direct aminolysis by a range of amines to afford the corresponding 4-oxo-4H-quinolizine-2-carboxamides 4a-i in moderate to good yields.