assembly of 2-substituted benzimidazoles and 2-benzimidazolones has been developed. Under very mild copper catalysis or transition metal-free conditions, a wide range of the 2-alkyl/alkenyl benzimidazole derivatives can be conveniently and selectively synthesized through the domino reactions of o-haloarylcarbodiimides with active methylene species. Interesting complimentary effect was discovered under the