Pyrano[2,3-c]pyrazoles are obtained via mixing ethyl acetoacetate, hydrazine hydrate, aldehydes or ketones and malononitrile in the absence of solvent. These same products were also obtained by reacting arylidenemalononitriles 3 with 3-methyl-2-pyrazolin-5-ones. NOE difference experiments confirmed that these products exist solely in the 2H form. Similar treatments of 3-amino-2-pyrazolin-5-one with arylidene-malononitrile afforded adduct 6. Similarly mixing ethyl cyanoacetate, hydrazine hydrate, aldehydes, with malononitrile gave the same product 6. A novel synthesis of 4-oxo-4H-pyrano[2,3-c]pyrazole (8) could be achieved via reacting 3-methyl-2-pyrazolin-5-one with a mixture of cyanoacetic acid and acetic anhydride. Similar treatment of 3-aminopyrazole 11 with the benzylidene-malononitrile produced the pyrazolo[2,3-a]pyrimidines 12a,b.

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2-Cyanoacetyl-1-methylpyrrole 1 reacts with acetylacetone in glacial acetic acid in presence of ammonium acetate to yield a polysubstituted pyridine derivative 5. In contrast, ethyl acetoacetate reacts with 1 to yield a pyranone derivative 8, formed via a rearrangement process. Enaminonitrile 3, generated by reaction of 2-cyanoacetyl-1-methylpyrrole 1 with the dimethylformamide dimethylacetal (DMFDMA), undergoes condensation with malononitrile to yield a 2-dialkyl-aminopyridine again via a rearrangement pathway. Structural assignments to 2-cyanoacetyl-1-methylpyrrole 1, enaminonitrile 3, pyrrole-substituted pyran 8, and pyridine 14 were made using X-ray crystallographic analysis. Finally, 2-cyanoacetyl-1-methylpyrrole 1 undergoes coupling with benzenediazonium chloride to yield the arylhydrazone 2 that reacts with hydroxylamine hydrochloride to yield an amidoxime 19 that participates in ready cyclization to form the pyrrole-substituted 1,2,3-triazole 20 whose structure could be also established by X-ray crystallography.