Electrochemical gold-catalysed biocompatible C(sp2)–C(sp) coupling

Gold-catalysed oxidative coupling reactions often require strong oxidants because of the high redox potential of Au(i)/Au(iii) (1.41 V versus the saturated calomel electrode), resulting in poor reaction economy and functional group compatibility. Here we report a dinuclear gold-catalysed C(sp2)–C(sp) coupling reaction between structurally diverse alkynes and arylhydrazines under electrochemical conditions. This approach provides a practical oxidative C–C coupling reaction that avoids the use of synthetic oxidants and instead produces H2. This method exhibits excellent functional group compatibility towards compounds such as alcohols, amines, sulfides and electron-rich arenes, which possess functional groups sensitive to oxidizing agents. This synthetic robustness is further shown by the successful late-stage modification of different kinds of alkynes tethered to biomolecules such as amino acids, peptides, nucleotides and saccharides. Mechanistic studies suggest a first aryl radical oxidative addition step with Au(i), followed by anodic oxidation to generate the highly electrophilic Ar–Au(iii) species for subsequent σ-activation of alkynes.