Efficient syntheses of 3H-azuleno[8,1-cd]pyridazines and their thermal and photochemical reactions

Azulenopyridazines 6 were efficiently synthesized from ethyl 4-hydrazinylazulene-1-carboxylate (2) using p-toluenesulfonic acid-catalyzed imine formation and intramolecular cyclization followed by dehydrogenation with KOH/MeOH in a one-pot operation. Thermal and photochemical reactions of azulenopyridazines 6 afforded 1-vinylazulenes 7 in good yields.