An efficient construction of imidazole ring by a Cs2CO3-promoted annulation of amidoximes with terminal alkynes in DMSO has been developed. This protocol provides a simple synthetic route with high atom-utilization for the synthesis of 2,4-disubstituted imidazoles in good yields under transition-metal-free and ligand-free conditions. Internal alkynes can also undergo the annulation to give 2,4,5-trisubstituted imidazoles.
Keywords: 2,4-disubstituted imidazoles; alkynes; amidoximes; annulation; base-promoted.