Microwave‐Assisted Synthesis of Bis(enaminoketones): Versatile Precursors for Novel Bis(pyrazoles) viaRegioselective1,3‐Dipolar Cycloaddition with Nitrileimines

Abstract

Synthesis of bis(enaminones) 6a, 6b, 6c and 7a, 7b, 7c was accomplished by the reaction of bis(acetophenones) 3a, 3b, 3c and 4a, 4b, 4c with dimethylformamide–dimethylacetal, under microwave irradiation. 1,3‐Dipolar cycloaddition of bis(enaminones) 6a and 7b, 7c with nitrileimines in refluxing benzene led to the regioselective synthesis of the novel bis(pyrazoles) 11a, 11b, 11c, 11d, 11e, 11f, 11g, 11h in 62–89% yield. The bis(pyrazoles) 11b, 11c underwent condensation with hydrazine hydrate to give the corresponding bis(pyrazolo[3,4‐d]pyridazines) 14a, 14b in good yields.