Copper-Catalyzed [3 + 2] Cycloaddition/Oxidation Reactions between Nitro-olefins and Organic Azides: Highly Regioselective Synthesis of NO₂-Substituted 1,2,3-Triazoles

A new copper-catalyzed [3 + 2] cycloaddition/oxidation reaction of nitro-olefins with organic azides has been developed to afford 1,4(-NO2),5-trisubstituted 1,2,3-triazoles. This reaction sequence has a broad substrate scope and affords NO2-substituted 1,2,3-triazoles with high regioselectivities and in good to excellent yields. The involved oxidative process overcomes the elimination of HNO2 for general cycloaddition of nitro-olefins with organic azides, which shows a high atom economy and potential applications.