Synthesis of 2,2′-bipyridyl derivatives using aza Diels–Alder methodology

Amidrazone 1 and the tricarbonyl derivatives 2a–c gave the triazines 3a–c, respectively, which reacted with 2,5-norbornadiene 4 in boiling ethanol yielding the corresponding novel 2,2′-bipyridines 5a–c in good yield. Triazine 6 gave the 2,2′-bipyridyl derivative 7 (65%) with compound 4 in 1,2-dichlorobenzene at 140°C.