Arenediazonium tetrachlorocuprates(II). Modification of the Meerwein and Sandmeyer reactions

Abstract In the copper-catalysed reactions of arenediazonium chlorides with unsaturated compounds arenediazonium tetrachlorocuprates(II) are formed as intermediates. A general method of preparation of these complexed diazonium salts is described. In polar solvents these salts undergo chlorinative dediazoniation to give chloroarenes in high yield. The reaction of an arenediazonium tetrachlorocuprate(II) with an activated alkene results in the same products as the Meerwein reaction. A radical cation mechanism for this reaction is proposed.