Reaction of some 1,2-diaza-1,3-butadienes with activated methine compounds. A straightforward entry to 1,4-dihydropyridazine, pyridazine, and 4,5(4H,5H)-cyclopropylpyrazole derivatives

1-Aminocarbonyl-1,2-diaza-1,3-butadienes with beta-tri- or beta-dicarbonyl compounds containing at least two keto functions give 1,4-dihydropyridazine s, while hydrazone 1,4-adducts are obtained in the case of compounds contai ning one or no keto function. 1,4-Dihydropyridazines are transformed into p yridazines. The same substrates with 3-phenoxypentane-2,4-dione afford pyri dazines. Surprisingly, 1-alkoxycarbonyl-1,2-diaza-1,3-butadiene with methyl 2-acetylacetoacetate produce 1-alkoxycarbonyl-4,5(4H,5H)-(alkoxycarbonylcy clopropyl)pyrazoles deriving from 1-alkoxycarbonyl-1,2-dihydropyridazine in termediates by ring contraction. These pyrazole derivatives with acetic aci d show ring expansion to 1-alkoxycarbonyl-1,4-dihydropyridazines that can b e converted into 1,4-dihydropyridazines with sodium hydroxide. 1-Alkoxycarb onyl-4,5(4H, 5H)-(alkoxycarbonylcyclopropyl)pyrazoles or 1-alkoxycarbonyl-1 ,4-dihydropyridazines with trifluoroacetic acid provide 1-aminopyrroles via 1-alkoxycarbonyl-1,4-dihydropyridazine intermediates in the case of pyrazo les. The X-ray crystal structure of 1-tert-butoxycarbonyl-3,5-dimethyl-4-me thoxycarbonyl-4,5(4H,5H)-(methoxycarbonylcyclopropyl)-1H-pyrazole was deter mined.