HETEROCYCLES

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■ Ring Transformations of Heterocycles over Synthetic Zeolites

Yoshio Ono*

*Department of Chemical Technology, Faculty of Engineering, Tokyo Institute of Technology, 2-12-1,Oh-Okayama, Meguro-ku, Tokyo 152-8552, Japan

Abstract

Synthetic zeolites are found to be very effective and selective catalysts for the vapor phase ring transformations of oxygen-containing heterocycles into nitrogen or sulfur-containing heterocycles. For example, tetrahydrofuran is converted into pyrrolidines and tetrahydrothiophene, while γ-butyrolactone is converted into pyrrolidinones and γ-thiobutyrolactone by the reactions with primary amines and hydrogen sulfide, respectively. The most effective catalysts differ with reactions. For the reaction of tetrahydrofuran with ammonia, acidic zeolites such as HL(proton form of L-type zeolite) are most effective, while for the reaction of γ-butyrolactone with hydrogen sulfide, basic zeolites like CsY(CS⁺ exchanged Y-type zeolite) are highly active. The kinetics of the ring transformations are studied and the reaction mechanisms are discussed.