11-24-03 16:40
No 472871
Heck Reaction over Pd-Loaded ETS-10 Molecular Sieve
Bulletin of the Chemical Society of Japan Vol. 76 No. 10, pp.1989-1992,2003
DOI:10.1246/bcsj.76.1989
http://www.jstage.jst.go.jp/article/bcsj
Abstract.A palladium-loaded ETS-10 molecular sieve has been used as a catalyst in Heck reaction. The catalyst exhibits high activity and selectivity towards the carbonÐcarbon coupling of aryl halides with olefins, even at low concentrations of Pd (0.009 to 1.4 mol% with respect to the substrate). In the case of the coupling of ethyl acrylate with iodobenzene, 96% conversion of iodobenzene with greater than 98% selectivity could be obtained within 1 h over a 0.2 wt % Pd-loaded catalyst. The catalyst activates aryl bromide and chloride substrates, and appears to be heterogeneous. The reaction has been investigated with different alkyl halides, olefins and bases.
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Conclusion
Pd-ETS-10 (reduced in H2) exhibits a high activity towards the Heck coupling of aryl iodides with acrylates under the typical reaction conditions. ATON value of 10000 is achieved for a 0.2 wt % Pd-ETS-10 catalyst for iodobenzene. Though a small amount of Pd leaches out into solution when iodobenzene is used as the substrate and DMF as a solvent, the reaction is found to proceed mainly by a heterogeneous route. When 1- bromo-4-nitrobenzene is used as the substrate, the reaction is totally heterogeneous. Aryl bromide, chloride and their derivatives exhibit moderate activity with ethyl acrylates. Organic
bases lead to higher catalytic activity than inorganic bases.The catalysts can be reused and reactivated by washing with a moderate decrease in activity. The substrate reactivity increases with electron-withdrawing substituents.
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