An investigation of the two-step nature of the Sandmeyer reaction

Abstract

The roles of the reductant and of the ligand transfer agent in the Sandmeyer reaction are examined. Several new reducing agents, namely Sn²⁺, Fe²⁺, ferrocene, Fe(CN)₆^4–, and ascorbic acid are shown to be able to stimulate bromo- and chloro-dediazoniation. The procedure is of potential synthetic interest in that the reaction occurs smoothly at room temperature. The efficiency of the process depends on the redox potential of the reductant and the presence of a potential threshold of ca. 1 V is detected, above which the reaction does not occur. Evidence for the non-catalytic role of the reductant are presented. Comparison with the iodide stimulation case is also discussed.