Catalytic applications of {[HMIM]C(NO2)3}: as a nano ionic liquid for the synthesis of pyrazole derivatives under green conditions and a mechanistic investigation with a new approach

Abstract

Catalytic applications of 1-methylimidazolium trinitromethanide {[HMIM]C(NO₂)₃}as the first nano ionic liquid (NIL) was studied. The described NIL was efficiently tested in the synthesis of 5-amino-pyrazole-4-carbonitrile derivatives in good to excellent yields on the three-component condensation of various aromatic aldehydes, malononitrile and phenylhydrazine at room temperature under solvent-free and ambient conditions. In the next study, 1,4-dihydropyrano-[2,3-c]-pyrazole derivatives were also synthesized via four-component condensation of a good range of aromatic aldehydes, malononitrile, phenylhydrazine and ethyl acetoacetate in the presence of NIL under the same reaction conditions. The described reactions were in good agreement with the green chemistry disciplines and their major advantages are short reaction times, good yields, ease of separation, recycling and reusability of NIL. A new mechanistic approach was proposed for the final step of the pyrazoles synthesis which was supported by theoretical studies.