Copper(I) oxide and benzoic acid 'on water': a highly practical and efficient catalytic system for copper(I)-catalyzed azide-alkyne cycloaddition

A simple combination of Cu2O and PhCO2H 'on H2O' has been developed as a highly practical and efficient catalytic system for copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). It not only provides a further evidence for the strategy of carboxylic acids-promoted CuAAC, but also offers significant advantages to CuAAC because Cu2O is one of the most stable and cheapest Cu(I) sources; PhCO2H is one of the structurally simplest bidentate ligands; and water is the most 'green' solvent.