Copper iron oxide promoted cascade annulation between 2′-nitrochalcones and NH pyrazoles

Abstract

Synthesis of 3-aminoindole derivatives via a cascade coupling of 2′-nitrochalcones and NH bonds in pyrazoles under the assistance of copper iron oxide is firstly reported. Our approach would provide an alternative to avoid the requirement of strong base and/or unrecoverable transition metal salt. Characterization of the spent copper iron oxide by XRD, FT-IR, and N₂ physisorption revealed that the structure of the material did not change during the reaction. Scope of the substrates was also attempted, confirming the compatiblity of several weakly-nucleophilic pyrazoles.