Double Intramolecular Diels—Alder Reaction of α,β-Unsaturated Hydrazones: A New Route to 2,2′-Bipyridines.

Heating the 1,3-diynyl bis-α,β-unsaturated hydrazones 3, 6 and 10 results in double intramolecular Diels–Alder reaction of the 1-azadienes, and after aromatisation by loss of dimethylamine, the formation of bipyridines 11–14.