Mechanistic Investigation of the Copper-Catalyzed Reactions of Diphenyliodonium Salts

Article abstract of DOI:10.1021/ja00345a045

The reaction of diphenyliodonium hexafluoroarsenate (PIFA) with copper(II) benzoate in alcohol solvent gives iodobenzene and alkyl phenyl ether, the arylation product, in high yield along with small amounts of phenyl benzoate and benzene.With diphenyliodonium bromide (PIBr), a substantial yield of bromobenzene is obtained along with iodobenzene and ether.In nonnucleophilic solvent, CH2Cl2, PIFA yields appreciable amounts of iodobenzene, benzene, biphenyl, and phenyl benzoate.In CH2Cl2 PIBr gives a high yield of bromobenzene and iodobenzene and low yields of benzene and biphenyl.Cu^I is shown to be the catalytically active oxidation state of copper, based in part on the chemistry observed with independently prepared copper(I) benzoate.Phenyl radical intermediates are ruled out in the reactions of PIFA and PIBr in methanol and CH2Cl2, and their chemistry is contrasted with that observed with a benzenediazonium salt.A mechanism involving a phenylcopper(III) intermediate is proposed which concisely accounts for the reaction products observed with PIFA and PIBr in both nucleophilic and nonnucleophilic solvents.