Regiodivergent Cyclotrimerization of Alkynes: Switchable Selectivities by Iron and Nickel Catalysts.

Metal-catalyzed strategy for cyclotrimerization of alkynes to form trisubstituted benzenes is critically important for organic synthesis. Although a significant advancement has been achieved in this area, switchable regioselectivity and controlled regiodivergent of products for the cyclotrimerization of alkynes is a longstanding challenge, especially based on nonexpensive earth-abundant metals. Herein, we report a metal-source-regulated strategy for the regioselective synthesis of two cyclotrimerization regioisomers from a wide range of alkynes. This method achieves precise regiocontrol in the alkyne cyclotrimerization reaction. By utilizing a cooperative catalytic system composed of a commercially available iron and nickel-catalytic system and pinacolborane (HBpin), 1,2,4-trisubstituted benzenes or 1,3,5-trisubstituted benzenes can be stereoselectively synthesized. Notably, this protocol features mild reaction conditions (30-80 °C), a broad substrate scope (including aryl, alkyl, and silyl derivatives), and a low-cost, commercially available catalyst system. The critical advantages of this strategy overcome the practical limitations of existing high-temperature or expensive catalytic systems.