Selective di- and monochlorination of pyridazine-annelated bis(imidazolium) salts

A synthetic route for the selective di- and monochlorination of pyridazine annelated bis(imidazolium) salts at the formamidinium moieties with trichloroisocyanuric acid (TCCA) is presented. Due to the steric hindrance, the molecular structure of the dichlorobis(imidazolium) salt shows a pronounced torsion from planarity as well as a deviation of the C-Cl bond vectors from the ideal bisecting line of the respective NCN angles such as to avoid each other. The monochlorinated bis(imidazolium) salt is free of steric hindrance and therefore shows less deviation from the parent bis(imidazolium) salt. In the presence of acetate the chloroimidazolium salt acts as a chlorination agent for acetate leading to formation of acetyl chloride and the respective urea.