Phenacyl Bromides Revisited: Facile Synthesis of Some New Pyrazoles, Pyridazines, and Their Fused Derivatives (original) (raw)

Journal of Heterocyclic Chemistry, 2013

Abstract

Phenacylmalononitriles 8a, 8b react with hydrazines under dry conditions to afford the pyrazole derivatives 9a, 9b, 9c, 9d and in refluxing dioxane to afford the pyrazolo[3,4-c]pyridazine derivatives 11a, 11b, 11c, 11d and the pyridazine-6-imine derivatives 12a, 12b, 12c, 12d. Compounds 12a, 12b were transformed into their oxo analogs 13a, 13b upon reflux in ethanolic HCl, whereas 12c, 12d were transformed into the furan derivatives 14a, 14b under the same reaction conditions (reflux in ethanolic HCl). Compounds 8a, 8b could be transformed directly into the benzoyl-pyrazole derivatives 16a, 16b, 16c, 16d upon coupling with diazotized aromatic amines in pyridine. The structures of the new compounds were substantiated by elemental analyses and spectral data as well as x-ray crystallographic analysis. Plausible mechanisms for the unexpected transformations are suggested.

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