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[Related articles/posters: 104 019 087 ] |
Zeolites, a class of cristalline alumosilicates, attracted much attention of organic chemists over the last decade. Due to their regular microporous structure they proved to be useful as a tool for reaction control in fine organic synthesis [1]. Heterocyclic community, however, seem not to be involved very much into the exploration of new synthetic possibilities provided by these materials.
Iododerivatives of thiophenes and furans are usually obtained via iododemetallation reaction [2] or via direct iodination of corresponding heteroaromatics in the presence of oxidants (mineral acids, mercury oxide) [3, 4]. It has been reported on the use zeolites for direct iodination of aromatic compounds [5]. We now extend this approach to iodination of heteroaromatics.
2. RESULTS
In this study we have investigated reaction:
Results obtained are given in the table:
| Compound | Iodinating agent | Zeolite | Convertion, % (GLC) |
| Thiophene | I2 | CuY | 83 |
| Methyl ester of
2-thiophenecarboxylic acid |
ICl | NaY | 50 |
| 2-isobutirylfuran | I2 | CsY | 67 |
3. EXPERIMENTAL
To a stirred mixture of a heterocyclic compound (4 mmol), precalcined zeolite (5 g) and methylene chloride (20 ml) 4 mmol of iodinating agent was added. The suspension was stirred for several hours at room temperature, then zeolite was filtered off and washed with methylene chloride. The filtrate was washed with aqueous sodium thiosulfate and water. The organic layer was dried with calcium chloride. The products were identified by 1H NMR and GLC.
References
1. W. Holderich, M. Hesse and F. Naumann, Angew. Chem., Int. Ed. Engl., 27 (1988) 226.
2. B.J. Wakefield, Organolithium Methods, Acad. Press, London, 1988.
3. H.Y. Lew and C.D. Noller, Org. Synth., Coll. Vol. IV (1953) 545.
4. W. Minnis, Org. Synth., Coll. Vol. II (1943) 357.
5. a). E.A. Zubkov and V.G. Shubin, Internat. Symp. on Zeolites in China, Nanjing 1995, Proceedings, 2-205.