Recyclable Polyethylene Glycol Ubiquinol Succinate-Bound N-Heterocyclic Carbene–Gold(I) Complexes: Sustainable Micellar Catalysis in Water

An efficient synthesis of three amphiphilic polyethylene glycol ubiquinol succinate (PQS)-bound N-heterocyclic carbene (NHC)–gold(I) complexes as micellar catalysts in bulk water was developed. The surfactant-bound gold catalysts were applied in three different cyclization reactions of acetylenic or allenic substrates, with the main focus being the gold-catalyzed dehydrative cyclization of alkynediols to furans. An effective recycling of the designer surfactant-bound NHC–gold(I) catalysts in water was demonstrated for all cyclization reactions. With sodium dodecyl sulfate as the cosurfactant, a significant acceleration of the catalytic reactions was observed. Mechanistic investigations of the gold-catalyzed dehydrative cyclization of alkynediols point to possible causes for this acceleration effect.