Silver(I)-Catalyzed C-X, C-C, C-N, and C-O Cross-Couplings Using Aminoquinoline Directing Group via Elusive Aryl-Ag(III) Species

摘要

Cross-coupling transformations are a powerful tool in organic synthesis. It is known that this kind of transformation undergoes 2-electron redox processes, and, for this reason, silver has been nearly forgotten as catalyst for cross couplings because silver is mainly considered as a 1-electron redox metal. Herein, we disclose effective Ag(I)-catalyzed cross coupling transformations using bidentate aminoquinoline as a directing group toward different nucleophiles to form C-C, C-N, and C-O bonds. DFT calculations indicate the feasible oxidative addition of L-I-I substrate via the Ag(I)/Ag(III) catalytic cycle. Furthermore, ion spectroscopy experiments suggest a highly reactive aryl-Ag(III) that in the absence of nucleophiles reacts to form an intermolecular cyclic product [Sd-Ag(I)-CH3CN], which in solution forms Sa. This work proves that silver can undergo 2-electron redox processes in cross-coupling reactions like Pd and Cu.