Gold(I) Catalysis at Extreme Concentrations Inside Self-​Assembled Nanospheres

Homogeneous transition‐metal catalysis is a crucial technology for the sustainable preparation of valuable chemicals. The catalyst concentration is usually kept as low as possible, typically at mM or μM levels, and the effect of high catalyst concentration is hardly exploited because of solubility issues and the inherent unfavorable catalyst/substrate ratio. Herein, a self‐assembly strategy is reported which leads to local catalyst concentrations ranging from 0.05 M to 1.1 M , inside well‐defined nanospheres, whilst the overall catalyst concentration in solution remains at the conventional mM levels. We disclose that only at this high concentration, the gold(I) chloride is reactive and shows high selectivity in intramolecular C—O and C—C bond‐forming cyclization reactions.