Leaching-Free Supported Gold Nanoparticles Catalyzing Cycloisomerizations under Microflow Conditions

A continuous-flow protocol for the gold-catalyzed cycloisomerization of sterically hindered Ugi-adducts to spiroindolines in a packed-bed reactor is presented. Spiroindolines with various substitution patterns are formed in good yields and with good selectivity. A detailed characterization of the catalyst deactivation process was conducted, whereas no metal leaching from the catalyst was detected.