ORGN 453 |
| Water-soluble metal catalysts have been synthesized that allow cross-coupling reactions to be carried out in water/organic biphasic solvent systems. Tri(2,4-dimethyl-5-sulfonatophenyl)phosphine trisodium salt (TXPTS), tri(4-methoxy-2-methyl-5-sulfonatophenyl)phosphine trisodium salt (TMAPTS), and (2-(di-t-butylphosphino)ethyl)trimethylammonium chloride (t-BuAmphos) all showed great success as catalyst precursors for coupling reactions. Both TXPTS and TMAPTS have proven to yield very active catalyst in Suzuki coupling even at catalyst concentrations as low as 0.05 mol%. TXPTS and TMAPTS also gave active catalysts in the Sonogashira coupling of electron deficient aryl bromides in the absence of a copper(I) promoter. Palladium catalysts derived from TXPTS are believed to be the first to allow Heck coupling of unactivated and deactivated aryl bromides under relatively mild conditions in aqueous solvents. Applying the catalyst derived from t-BuAmphos it has been shown that Sonogashira, Suzuki, and Heck coupling can be achieved for deactivated aryl bromides at high yields under mild reaction conditions. A series of water-soluble imidazolium salts and their silver and palladium carbene complexes have been synthesized and characterized by NMR spectroscopy. |
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Metal-Mediated Reactions and Syntheses
8:00 AM-12:00 PM, Wednesday, 29 March 2006 Georgia World Congress Center -- C302, Oral
Division of Organic Chemistry |