2-heteroylhydrazonopropanals 2a-e and 3-oxo-2-arylhydrazonopropanals 2f-k were prepared via coupling of enaminones 1 with aromatic diazonium salts. Compounds 2a-c condensed with hydrazine hydrate to yield the corresponding hydrazones 3a-c which afford on cyclisation the cinnoline derivatives 6a-c, while condensation of 2g, j with hydrazine hydrate directly yielded the pyrazole derivatives 4g-j. Condensation of 2a-c, f, g with phenyl hydrazine gave the corresponding phenyl hydrazone derivatives 7a-c, f, g. Structures of 2a, h and 3a were assessed by single crystal X-ray analyses.

The title compounds 3a-j were synthesized via coupling of enaminones 2a-d with aromatic diazonium salts. The reaction of 3b-f,h-j with dimethyl acetylenedicarboxylate and triphenylphosphine afforded dimethyl 2-aryl-6-aroyl-2,3-dihydropyridazine-3,4-dicarboxylates 7b-f,h-j. . The reaction of 3b,d,f,g with phenacyl bromide afforded 3-aroyl-5-benzoylpyrazoles 9b,d,f,g.,while compound 3i condensed with benzoylacetonitrile to yield pyridazin-6-imine 11.Reaction of 3c-e,h,j with p-toluidine yielded the enamineazo 12c-e,h,j. The structures of 7b,d,i and 9b were confirmed by X-ray crystal structure determination.

Pyridazine derivatives R 0500 Substituted Hydrazonals as Building Blocks in Heterocyclic Synthesis: A New Route to Arylhydrazonocinnolines. -A novel synthesis for the hydrazonocinnolines (V) is reported and the different reactivity of the hydrazonopropanals (III) in the reaction with hydrazine is discussed. -(AL-SHIEKH, M. A.; MEDRASSI, H. Y.; ELNAGDI, M. H.; HAFEZ*, E. A.; J. Chem. Res. 2007, 7, 432-436; Dep. Chem., Fac. Sci., Cairo Univ., Giza 12613, Egypt; Eng.) -H. Haber 03-155