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Issue 11, 2008
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Thermoregulated aqueous biphasic catalysis of Heck reactions using an amphiphilic dipyridyl-based ligand

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Abstract

A neat water-based thermoregulated system for Pd-catalyzed Heck reactions is described. It uses a thermo-responsive ligand L that enables (1) the transfer of the catalyst in the organic phase upon heating thus allowing the reaction to take place in one phase, and (2) the separation/recovery of the catalyst in the water phase upon cooling and hence catalyst reuse. The amphiphilic ligand L with an inverse temperature-dependent solubility in water is prepared by covalent attachment of 2,2′-dipyridylamine to the tip of a nonionic polyoxyethylene surfactant (decyloctaethyleneglycol C10E8). Spectroscopic studies reveal that the amphiphilic dipyridyl-based ligand L forms a 1 : 1 Pd complex (PdLCl2) in organic solvent and a 1 : 2 Pd complex in water. Cross-coupling reactions of iodobenzene with ethyl acrylate and styrene are achieved, without any organic solvent, at 100–120 °C with sodium carbonate as a base using 0.1 to 0.5 mol% of Pd catalyst generated in water from L and Na2PdCl4. The reaction products, trans-cinnamic acid and stilbene, are readily isolated at room temperature, and the catalyst is recovered in the aqueous phase, without the need to add any organic solvent. The aqueous phase can be used in three catalytic runs with an almost constant catalytic activity for the coupling of iodobenzene with ethyl acrylate.

Graphical abstract: Thermoregulated aqueous biphasic catalysis of Heck reactions using an amphiphilic dipyridyl-based ligand

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Article information


Submitted
20 Mar 2008
Accepted
11 Aug 2008
First published
07 Oct 2008

Green Chem., 2008,10, 1197-1203
Article type
Paper

Thermoregulated aqueous biphasic catalysis of Heck reactions using an amphiphilic dipyridyl-based ligand

H. Azoui, K. Baczko, S. Cassel and C. Larpent, Green Chem., 2008, 10, 1197
DOI: 10.1039/B804828B

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