External oxidant-free, ligand-assisted heterogeneous gold-catalyzed C(sp2)‒C(sp) cross-coupling of aryldiazonium salts with terminal alkynes

Abstract

A new mesoporous silica SBA-15-immobilized triphenylphosphine-gold(I) complex [Ph3P-SBA-15-AuNTf2] was synthesized via the addition of (2-(diphenylphosphino)phenyl)methanamine to triethoxy(3-isocyanatopropyl)silane, followed by immobilization onto SBA-15 and then the reaction with Me2SAuCl and AgNTf2, respectively, and was characterized by different physico-chemical techniques. In the presence of 5 mol% of Ph3P-SBA-15-AuNTf2 and 20 mol% of 2,2'-bipyridine (bpy) as a ligand, the C(sp2)-C(sp) cross-coupling reaction of aryldiazonium tetrafluoroborates and terminal alkynes proceeded smoothly in acetonitrile at room temperature without an external oxidant to deliver diverse arylalkynes in good to excellent yields with wide tolerance of functional groups, including aryl iodide or bromide incompatible with classical cross-coupling. The new supported gold(I) complex could be readily recovered by centrifugation of reaction solution and reused more than ten cycles without any significant decrease in its catalytic activity.