The amount of palladium was from 1. The Heck reactions of iodobenzene with cyclohexene were carried out in a 50 cm 3 Schlenk tube with magnetic stirring. Afterwards, organic products were separated by extraction with diethyl ether twice with 10 cm 3 and analyzed by GC—MS Hewlett Packard A with dodecane 0. For reactions performed in DMF, diethyl ether 15 cm 3 was added, and a sample was quenched with water 10 cm 3.
Organic products were extracted from the water phase with diethyl ether 15 cm 3 , and a combined ether solution was analyzed by GC. Products 1, 2, and 3 were identified by comparison of their MS spectra with literature data [ 49 ]. The soluble palladium species, [Bu 4 N] 2 [PdX 4 ] complexes, and Pd 0 nanoparticles stabilized by tetrabutylammonium salt were most probably responsible for the observed reactivity. The same precursors used in DMF presented a very low catalytic activity. The same catalysts used in [Bu 4 N]Br presented a lower selectivity and produced 3-phenylcyclohexene 2 and 4-phenyl-cyclohexene 3 in comparable amounts, with a slight excess of 2.
Different results obtained in with homogeneous and heterogeneous precursors can be explained by the contribution in the reaction course of insoluble, supported palladium species besides of soluble ones. Excellent selectivity to 3 was also noted under such conditions. Sample Availability: Samples of the compounds are available from the authors. National Center for Biotechnology Information , U. Journal List Molecules v. Published online Mar Author information Article notes Copyright and License information Disclaimer.
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This article has been cited by other articles in PMC. Keywords: palladium, Heck coupling, heterogenized catalysts, cyclohexene. Introduction The Heck coupling, a C—C bond formation process also described as olefin arylation, is one of the most important palladium-catalyzed reactions [ 1 , 2 , 3 , 4 , 5 , 6 ].
Results and Discussion 2. Homogeneous catalysts The Heck reaction of cyclohexene with iodobenzene is presented on Figure 1. Open in a separate window. Figure 1. Figure 2. Diarylated products formed in the Heck reaction of cyclohexene with iodobenzene. Figure 3. Figure 4.
Heterogeneous catalysts For further studies, we selected heterogenized palladium catalysts obtained by impregnation of PdCl 2 on alumina-based oxides. Figure 5. Figure 6. Table 3 Results of the Heck coupling of iodobenzene with cyclohexene catalyzed by Pd supported on alumina-based oxides in DMF. Experimental 3. Preparation of alumina-based supports Alumina-based oxides were prepared by the sol-gel technique [ 41 , 42 ].
Palladium Reagents and Catalysts
Preparation of supported Pd II catalysts First, the support 0. Heck reaction procedure The Heck reactions of iodobenzene with cyclohexene were carried out in a 50 cm 3 Schlenk tube with magnetic stirring. Footnotes Sample Availability: Samples of the compounds are available from the authors. References and Notes 1. Heck R. Palladium-catalyzed reactions of organic halides with olefins.
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Bedford R. The development of palladium catalysts for C-C and C-heteroatom bond forming reactions of aryl chloride substrates. Peris E. Recent homogeneous catalytic applications of chelate and pincer N-heterocyclic carbenes. Gniewek A. Reetz M. Calo V. Pryjomska-Ray I. Base free efficient palladium catalysts of Heck reaction in molten tetrabutylammonium bromide. A: Chem. Glorius F. N-heterocyclic carbenes in transition metal catalysis.
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Heck reaction in ionic liquids catalyzed by a Pd-benzothiazole carbene complex. Jeffery T. Tetraalkylammonium salts in Heck-type reactions using an alkali-metal hydrogen carbonate or an alkali-metal acetate as the base. Biffis A.
Metallic palladium in the Heck reaction: active catalyst or convenient precursor? The reversible transfer of palladium between solution and support. Topics Catal. In situ generation of highly active dissolved palladium species from solid catalysts - a concept for the activation of aryl chlorides in the Heck reaction. Kleist W. Supported palladium as catalyst for carbon-carbon bond construction Heck reaction in organic synthesis. Design of highly active heterogeneous palladium catalysts for the activation of aryl chlorides in Heck reactions.
Palladium reagents and catalysts : innovations in organic synthesis / Jiro Tsuji - Details - Trove
Silica-supported palladium: sustainable catalysts for cross-coupling reactions. Silica-supported Pd catalysts for Heck coupling reactions. Djakovitch L.
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