Iron-Catalyzed Cyclotrimerization of Terminal Alkynes by Dual Catalyst Activation in the Absence of Reductants

Catalyzing C-C bond-forming reactions with earthabundant metals under mild conditions is at the heart of sustainable synthesis. The cyclotrimerization of alkynes is a valuable atom-efficient reaction in organic synthesis that is enabled by several metal catalysts, including iron. This study reports an effective iron-catalyzed cyclotrimerization for the regioselective synthesis of 1,2,4-substituted arenes (1 mol% catalyst, toluene, 20°C, 5 min). A dual activation mechanism (substrate deprotonation, reductive elimination) renders the simple FeII precatalyst highly active in the absence of any reductant.