液相有機合成反応へのゼオライトの新しい活用

概要

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Various cation-exchanged zeolites have been applied to organic reactions in a liquid-phase as an acid-base bifunctional catalyst (promoter), an efficient support for inorganic nucleophiles, and an inorganic, rigid ligand for transition metals. Alkali 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 ring-openings of epoxides. In those reactions acid sites and base sites on the zeolite surface prove to activate the reactants synergistically by our correlating the chemical properties of the zeolite with the chemical reactivities. Inorganic nucleophiles supported on calcium ion-exchanged zeolite induce the highly regioselective ringopenings of 2, 3-epoxy alcohols affected by the specific interaction of the epoxy alcohols with calcium ions in the zeolite. Cupric ions surrounded by the rigid framework of zeolite catalyze the decomposition of aryldiazomethanes to give cis-1, 2-diarylethylenes predominantly. In homogeneous, small pores of zeolites, organic reactions are found to proceed in a highly restricted way.