Catalytic C–S, C–Se, and C–P Cross-Coupling Reactions Mediated by a Cu^I/Cu^III Redox Cycle

Abstract

A well-defined macrocyclic aryl-Cu^III complex (<b>1</b>) readily reacts with a series of R–SH, Ar–SH, Ar–SeH, and (RO)₂(O)–PH (R = alkyl) nucleophiles to quantitatively afford the corresponding aryl alkyl thioethers, biaryl thioethers, biaryl selenide, and aryl dialkyl phosphonates, respectively. Competition experiments using bifunctional substrates revealed the important impact of lower p<i>K</i>_a values in order to discriminate between functional groups, although other influencing parameters such as steric effects have been identified. The catalytic version of these reactions is achieved using aryl bromide and aryl chloride model substrates, affording C–S, C–Se, and C–P coupling compounds in excellent to moderate yields. Low-temperature UV–vis and NMR monitoring of the reactions of complex <b>1</b> with a variety of nucleophiles support the formation of a ground-state <b>1</b>–nucleophile adduct. A mechanistic proposal for reaction of <b>1</b> with S-nucleophiles involving key nucleophile deprotonation and aryl-nucleophile reductive elimination steps is finally described