Regioselective Synthesis of 4,5-Diaryl-1-methyl-1H-imidazoles Including Highly Cytotoxic Derivatives by Pd-Catalyzed Direct C-5 Arylation of 1-Methyl-1H-imidazole with Aryl Bromides

Cyclopentyl methyl ether: an alternative solvent for palladium-catalyzed direct arylation of heteroaromatics

Some ethers, such as cyclopentyl methyl ether and di-n-butyl ether, which can be considered as "greener" solvents than N,N-dimethylacetamide (DMAc) or DMF, can be advantageously employed for the palladium-catalyzed direct arylation of heteroaromatics. In the presence of such ethers and only 0.5-1 mol % of palladium catalysts at 125-150 °C, the direct 5-arylation of thiazoles, thiophenes, or furans by using aryl bromides as coupling partners proceeds in moderate to high yields.

Palladium catalyzed direct 3-arylation of benzofurans using low catalyst loadings

The palladium-catalyzed direct 3-arylation of benzofurans provides a cost-effective and environmentally attractive route for the preparation of 3-arylbenzofuran derivatives. The reactions were carried out using a wide variety of electronically and sterically diverse aryl or heteroaryl bromides with low catalyst loadings. In the presence of only 0.1-0.5 mol % catalyst, products in moderate to good yields were obtained. The aryl bromide reactants were able to tolerate a wide range of functionalities, such as acetyl, propionyl, formyl, ester, nitrile, trifluoromethyl, or fluoro groups. Higher yields were obtained using electron-deficient aryl bromides as reactants compared to using electron-rich aryl bromides. Functionalized benzofuran derivatives, bearing formyl or hydroxymethyl on C2, were also successfully employed.