Chapter II.1 Novel Catalytic Functions of Zeolites in Liquid-Phase Organic Reactions

Abstract

Abstract Various cation-exchanged zeolites were applied to organic reactions in the liquid phase as acidic and basic bifunctional catalysts (promoters), as efficient supports for inorganic nucleophiles and as rigid metal ligands for regulating metal-catalysed reactions. Alkali metal cation-exchanged Y-type zeolites promote nucleophilic substitution reactions such as O-benzylation of alcohols with benzyl chloride, selective N-monoalkylation of anilines with alkylating agents and nucleophilic ring openings of epoxides with amines. In these reactions, acidic and basic sites on the zeolite surface prove to activate the reactants synergistically through the correlation of the chemical properties of the zeolite with the chemical reactivities. Inorganic nucleophiles such as NaN 3 , NH 4 Cl, NH 4 Br and NaSPh can be highly activated when finely dispersed on a strongly acidic zeolite CaY, and the CaY-supported nucleophiles are found to bring about highly regioselective ring openings of 2,3-epoxy alcohols through the specific interactions of the epoxy alcohols with calcium ions in the zeolite. Reactive molecular bromine is readily modulated by being adsorbed on zeolite 5A to give a selective brominating agent for aromatic amines. Copper (II) ions surrounded by the solid framework of zeolite catalyse stereoselective dimerizations of aryldiazomethanes to give predominantly cis-1,2-diarylethylenes. In uniform and small pores of zeolite, organic reactions are found to proceed in a much more restricted way than in solutions.