Polyfunctional Aliphatic Compounds. V. The Cyclization of Dinitriles by Halogen Acids. A New Synthesis of Imidazoles

Dinitriles having the general structure, RN(CN)CH(CN)R, undergo cyclization to 2-bromo-4(5)-aminoimidazoles when treated with anhydrous hydrogen bromide. Where R and R′ are aryl groups these amino compounds are generally stable enough to be isolated as the free bases. Otherwise, the imidazoles can be obtained as their acetamino derivatives. A convenient method for the synthesis of the previously unavailable starting dinitriles utilizes the reaction of a monosubstituted cyanamide with an α-haloalkyl, or an α-[4-toluenesulfonyloxyl] alkyl cyanide in anhydrous dimethylformamide using triethylamine as an acid acceptor.