Synthesis of pyridine derivatives using aza Diels–Alder methodology

Amidrazone 1 reacted with the unsymmetrical tricarbonyls 2a, 2c and 2d giving triazines 3a, 3c and 3d, respectively. These triazines were converted into their corresponding pyridine derivatives 6a, 6c and 6d in aza Diels–Alder reactions with 2,5-norbornadiene 5. Triazines 3c and 3d gave the pyridolactones 9c and 9d with 2,3-dihydrofuran.