Microwave-Assisted Synthesis of Ethyl 1,3-Disubstituted-1,6-dihydropyrrolo[2,3-c]pyrazole-5-carboxylates

A novel series of ethyl 1,3-disubstituted-1,6-dihydropyrrolo[2,3-c]pyrazole-5-carboxylates can be rapidly and efficiently synthesized in excellent yields by condensing a variety of 1,3-substituted-4-formyl-5-chloropyrazole with ethyl isocyanoacetate in the presence of 1-methyl-3-butylimidazolium hydroxide under microwave irradiation. The simple experimental procedure, DMSO-free condition, short period of conversion, and excellent yields are the advantages of the present method. The structures of the novel compounds are confirmed by IR, ¹H NMR, ¹³C NMR, MALDI-TOF MS, and elemental analysis.