The microenvironment around a catalyst could have profound influence on catalysis. Gold clusters encapsulated within interfacially cross-linked reverse micelles catalyzed hydroamination of alkynes at room temperature instead of at 100 °C commonly required for gold nanoparticles. Different metal oxides introduced into the micelle core by sol–gel chemistry interacted with the gold clusters and modulated their catalysis, with silicon oxide being the most effective cocatalyst.