One-Pot Protocol for the Synthesis of Imidazoles and Quinoxalines using N-Bromosuccinimide

N-bromosuccinimide (NBS)-mediated one-pot, green, efficient and practical synthesis of substituted imidazoles and quinoxalines has been achieved by the reaction of styrenes with N-arylbenzamidines and o-phenylenediamines, respectively, in a water:1,4-dioxane mixture. The reaction involves formation of an alpha-bromo ketone as an intermediate in the presence of NBS and water, followed by condensation with the N-arylbenzamidine and o-phenylenediamine. Use of an inexpensive NBS as a bromine source as well as an oxidant, water as a solvent and readily available starting materials makes this protocol environmentally benign and economically viable. Substituted imidazoles and quinoxalines were obtained in good to excellent yields with wide functional group compatibility.