Supported Heck catalyst

More recently, Chang reported a ruthenium-based Heck-type reaction in DME/H20 (1 1) by using alumina-supported ruthenium catalysts.154... 

Supported palladium catalysts for fine chemicals synthesis are generally based on metal particles. Nevertheless, a few examples are reported of the use of supported complexes as catalysts for the Heck reaction (see Chapter 9.6). Nearly all the possible immobilization methods have been tested for this reaction. 

E.2. Supported Dendritic Catalysts for Carbonylation, Hydroesterification, Oxidation, and Heck Reactions... 

In experiments with a supported palladium catalyst, Pd/C, satisfactory yields were obtained without the use of phosphine ligands for the Heck reactions of aryl iodide with acrylonitrile, styrene, and methyl methacrylate in the ionic liquid [BMIM]PF6 (259). The addition of triethylamine improved the yields. The Pd/C remained in the ionic liquid only. The ionic liquid containing Pd/C can be reused as... 

Scheme 20 Immobilization of a Heck catalyst on a ROMP-derived monolithic support...

Fig. 21. Heck-type vinylation reaction with PolyHIPE-supported Pd catalyst...

Initial work indicates that dispersed metals may be used to promote a variety of organometallic reactions. The Heck Arylation proceeds smoothly over supported Pd catalysts while diene cyclizations can be catalyzed by dispersed Rh metal. The use of these heterogeneous species facilitates product isolation and permits the application of flow systems rather than batch reactors for these reactions. Frontier Molecular Orbital and mechanistic considerations indicate that these reactions take place on the coordinately unsaturated comer atoms on the metal surface. 

Choudary, B.M., Madhi, S., Chowdari, N.S., Kantam, M.L. and Sreedhar, B., Layered double hydroxide supported nanopalladium catalyst for Heck-, Suzuki-, Sonogashira-, and Stille-type coupling reactions of chloroarenes, J. Am. Chem. Soc., 2002, 124, 14127-14136. 

Applications of Suzuki and Heck cross-coupling reactions were adopted by Gallop and coworkers [131] to prepare diverse biaryl- and styryl-substituted (3-lactams on solid support. The catalyst system, [PdCl2(dppf)]-TEA, was found to be efficient to promote C-C bond formation around a (3-lactam template (Schemes 26 and 27). 

A supported palladium catalyst for the Heck reaction (5.13) could be reused several times with little loss in activity.39 Heterogeneous catalysts for the Heck reaction, such as palladium on silica and platinum on alumina can perform just as well in the Heck reaction as homogeneous catalysts.40... 

The newly invented polystyrene-supported palladacycle catalyst was prepared in six steps with high yields. The simple precipitation and filtration process to recycle the catalyst after model reactions for Heck, Suzuki, and Sonogashira reactions is noteworthy.[1]... 

F Zhao, BM Bhanage, M Shirai, M Arai. Heck Reactions of lodobenzene and Methyl Acrylate with conventional Supported Palladium Catalysts in the Presence of Organic and/or Inorganic Bases without Ligands. Chem Eur J 6 843-848,2000. 

Apart from palladium, nickel is also known to catalyse Heck vinylations [9-12]. A supported nickel catalyst was appUed for the Heck reaction of iodobenzene with butyl acrylate [13]. The supported aqueous-phase catalysis performed almost as well as the analogous homogeneous catalyst NiCl2(PPli3)2-Only the conversion was sHghtly lower. No leaching of metal into the product phase was observed (detection limit approx. 1 ppm). The immobihzed catalyst was successfully recycled three times without observing loss of activity and selectivity. 

Terminally functionalized PIB oligomers have been used in a thermomor-phic heptane/JV,N-dimethylacetamide mixture as supports for thermally stable SCS-Pd(II) Heck catalyst precursors. A PIB-supported SCS-Pd(II) Heck catalyst was prepared from the carboxyl-terminated PIB oligomer by the sequence of reactions shown in Eq. 61. The PIB-bound SCS-Pd(II) species 125 so ormed was then used to carry out Heck chemistry (Eq. 62). As was true for SCS-Pd(II) species on other polymers [154,155,162], this catalyst was only effective for aryl iodides or activated aryl bromides. However, the catalyst could be used through... 

A non-covalent immobilization of Heck catalyst on silica (SILP concept) has been realized by Hagiwara et al. [217]. They used a silica surface, supported with Pd(OAc)2 dissolved in [BMIM][PFe]. This catalyst was appUed to the Mizoroki-Heck reaction of aryl halides with acrylate without a ligand in n-dodecane as solvent. It was six times reused and the overall TON reached 68 400 (for more details see Section 5.6). 

Table 5.4 Supported Pd catalysts on carbon tested in Mizoroki-Heck reactions.

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