Silver(I) oxide nanoparticles as a catalyst in the azide–alkyne cycloaddition

1,3-Dipolar cycloadditions between a number of azides and monosubstituted acetylenes have been carried out in the presence of catalytic amounts of silver(I) oxide nanoparticles. 4-Substituted 1,2,3-triazoles were usually the only products, while the presence of electron-withdrawing groups onto the azide moiety caused a loss of regioselectivity giving mixtures of 4- and 5-substituted 1,2,3-triazoles. A novel catalytic cycle has been proposed to rationalize this latter 'non-click' behaviour.