Copper(I)-catalyzed cross -coupling reactions and their applications
The scope of our copper(I)-catalyzed synthesis of diaryl acetylenes have been extended to the synthesis of 2 classes of heterocycles; 2-aryl benzo[ b]furans and 2-aryl indoles, by the cross-coupling of aryl acetylenes to 2-iodophenol and 2-iodoaniline, respectively. In addition, we demonstrated the scope of the copper(I) catalysts in catalyzing the cross-coupling of vinyl iodides. The aryl acetylenes and aryl/alkyl thiols were successfully coupled to vinyl iodides to synthesize 1,3-enynes and vinyl sulfides, respectively, using the well-defined copper(I)-complexes based on triphenylphosphine and nitrogen chelating ligand such as phenanthroline and bipyridine. The advantages of these protocols over the conventional copper-based methods are their simplicity, generality, and high functional group tolerances. We also demonstrated improvements of copper-assisted method of CF3 coupling to aryl iodide using metal trifluoroacetate salt, this reaction is not known with palladium chemistry. The possible mechanism of copper(I)-catalyzed reaction is also discussed and the application of our copper(I)-catalyzed protocol to the synthesis of interesting materials in cases where palladium catalyst failed is also shown.