Cu-Al mixed oxide catalysts for azide-alkyne 1,3-cycloaddition in ethanol-water

Cu(Al)O mixed oxides, which are obtained by the calcination of Cu-Al layered double hydroxide (LDH), promote the formation of 1,2,3-triazoles from an alkyne-azide cycloaddition reaction (Huisgen-type reaction) with excellent yields using an EtOH-H2O mixture as the solvent under microwave heating. The yield of the reaction is the result of both heterogeneous and homogeneous catalytic processes, as a consequence of capturing Cu(II) from the material by sodium ascorbate. Although the appropriate reaction conditions were employed (EtOH-H2O, 80 degrees C, MW, 10 min), the reconstruction of LDH by the so-called memory effect was not observed.