The solid Cu-Reactor is a catalyst for copper-catalyzed azide-alkyne chemistry (CuAAC) which does not need to be dissolved during the reaction unlike other Cu catalyst (copperbromid, coppersulfat) for catalyzing it. For this reason, it has the advantage that the concentration of dissolved copper ions is very low and therefore it is an ideal choice for performing click reactions on copper sensitive material like RNA. Additionally the solid Cu-Reactor can easily be removed after the reaction is finished by simply removing it and does not need additional steps as soluble catalysts. For ideal working conditions a ligand as THPTA (BCMI-006) is needed to be added to the reaction mixture.