Fluoroponytailed Crown Ethers and Quaternary Ammonium Salts as Solid-Liquid Phase Transfer Catalysts in Organic Synthesis

Abstract

Fluorous derivatives of dibenzo-18-crown-6 ether were prepared, and then successfully applied in representative solid-liquid phase transfer catalysis reactions, which were performed in standard organic solvents, such as chlorobenzene and toluene, as well as in fluorous solvents, such as perfluoro-1,3-dimethylcyclohexane. It was clearly shown that properly designed fluoroponytailed crown ethers could promote the disintegration of the crystal lattice of alkali salts, and transfer anions from the solid surface into an apolar, non-coordinating perfluorocarbon phase, for phase transfer catalysis reactions in organic synthesis. Furthermore, 3,5-bis(perfluorooctyl)benzyl bromide and triethylamine were reacted under mild conditions to provide an analogue of the versatile phase transfer catalyst, benzyltriethylammonium chloride, containing two fluoroponytails. This fluoroponytailed quaternary ammonium salt was also successfully employed as a catalyst in a variety of organic reactions conducted under solid-liquid phase transfer catalysis conditions, without a perfluorocarbon phase. Thus, being both hydrophobic and lipophobic, fluorous crown ethers and ammonium salts, could be rapidly recovered in quantitative yields, and reused without loss of activity, over several reaction cycles.

Impact of the Discovery of Fluorous Biphasic Systems on Chemistry: A Statistical and Network Analysis

“…As was strikingly visible also from the statistical analysis, the invention of the biphasic fluorous systems induced many new ideas in different sectors of chemical sciences. We demonstrate this tendency by citing a few characteristic references from three leading scientists in the field, who showed also high betweenness centrality scores in Table (Dennis P. Curran ,− and Gianluca Pozzi − ) and in Table (John A. Gladysz − ).…”

"A Minireview of Phase-Transfer Catalysis and Recent Trends"

“…However, phase-transfer catalysis also has the disadvantage that it is hard to separate the product from the organic phase [7][8][9]. To solve this problem, researchers have proposed a three-insoluble in the organic or aqueous phase, a third phase can form, and once the third phase is created, the reaction rate increases dramatically [10][11][12][13][14][15]. Some common traditional phase-transfer catalysts are cyclic crown ethers [16,17], polyether [18][19][20][21], tertiary amines [22], etc.…”

Ion Aggregation and R3N+–C(R)–H···NR3 Hydrogen Bonding in a Fluorous Phase

“…We have been taking advantage of the low solubility of biological lipophilic compounds in fluorous matrixes − to develop ion-selective membranes with improved selectivities and reduced biofouling. Besides other fluorous membrane ISEs, − we reported on pH selective electrodes with fluorous membranes that contained highly fluorinated trialkylamine derivatives as ionophores .…”