Perfluorocarbon Soluble Crown Ethers as Phase Transfer Catalysts

Fluorous derivatives of dibenzo-18-crown-6 ether were readily prepared by means of metal-catalyzed cross-coupling reactions, and then successfully applied as catalysts in representative solid-liquid phase transfer catalysis (PTC) reactions, which were performed in standard organic solvents, such as chlorobenzene and toluene, and also in fluorous solvents, such as perfluoro-1,3-dimethylcyclohexane (PFDMC). It was clearly shown that properly designed fluoroponytailed crown ethers can promote the disintegration of the crystal lattice of alkali salts and transfer anions from the solid surface into an apolar, non-coordinating perfluorocarbon phase. Far from being a simple chemical curiosity, this unprecedented observation has relevant implications in the design of PTC scenarios of wide applicability. This new paradigm represents an advance in crown ether chemistry, and their use as recyclable phase transfer catalysts.