The Sandmeyer reaction is a chemical reaction used to synthesize arylhalides from aryl diazonium salts. It is named after the Swiss chemist Traugott Sandmeyer. The reaction is a method for substitution of an aromatic amino group via preparation of its diazonium salt followed by its displacement with a nucleophile, often catalyzed by copper(I) salts. The nucleophile can include halide anions, cyanide, thiols, water, and others. The reaction does not proceed well with the fluoride anion, but fluorination can be carried out using the related Balz–Schiemann reaction.
Several improvements have been made to the standard procedures.
The majority of variations of the Sandmeyer reactions consist of using various copper salts. For example, using cuprous cyanide produces benzonitriles. Substituting thiols or water for the copper salts generates thioethers or phenols, respectively.
^M. P. Doyle, B. Siegfried and J. F. Dellaria (1977). "Alkyl nitrite-metal halide deamination reactions. 2. Substitutive deamination of arylamines by alkyl nitrites and copper(II) halides. A direct and remarkably efficient conversion of arylamines to aryl halides". J. Org. Chem.42 (14): 2426–2431. doi:10.1021/jo00434a017.