Ultrasound-promoted N-alkylation of imidazole. Catalysis by solid-base, alkali-metal doped carbons

The synthesis of N-substituted imidazoles via alkylation of imidazole with 1-bromobutane by sonochemical and thermally-activated reactions over two alkali-metal promoted carbons (Na+- and Cs+-Norit) as catalysts is reported. In this green, solvent free procedure, N-substituted imidazoles are produced exclusively in very high yields ( > 80%) when the Cs+-Norit carbon is employed under ultrasound activation. The basicity of the alkali metal cation increases the conversion and ultrasound activation affords a remarkable increase in the yields.