External oxidant-free heterogeneous gold-catalyzed C(sp2)–C(sp2) cross-coupling of aryldiazonium salts and arylboronic acids with the assistance of a bpy ligand

Abstract

A new mesoporous SBA-15-anchored (triazole)(triphenylphosphine)gold(I) complex [SBA-15-TAAu(PPh₃)OTf] was synthesized via immobilization of commercially readily available (4-(chloromethyl)phenethyl)trimethoxysilane onto SBA-15 and then the reactions with benzotriazole and Ph₃PAuOTf, respectively, and was characterized using different physico-chemical techniques. In the presence of 10 mol% of SBA-15-TAAu(PPh₃)OTf and 20 mol% of 2,2′-bipyridine (bpy) as a ligand, the C(sp²)–C(sp²) cross-coupling of aryldiazonium tetrafluoroborates and arylboronic acids proceeded effectively in MeCN at room temperature with Na₂CO₃ as the base without an external oxidant to afford diverse valuable biaryls in mostly good to excellent yields with wide tolerance of functional groups, including aryl iodide or bromide incompatible with traditional Suzuki–Miyaura coupling. The new heterogenized gold(I) complex could be facilely recovered by centrifugation of the reaction mixture and recycled for more than eight cycles with almost consistent catalytic efficiency.