Cu(I)-Catalyzed Three-Component Annulation for the Synthesis of 3-Acyl Imidazo[1, 5- a ]Pyridines from 2-Pyridinyl-Substituted p -Quinone Methides, Terminal Alkynes, and TsN 3 Using O 2 as the Oxygen Source.

Currently, most conventional methods to achieve imidazo[1,5- a ]pyridines have limitations for the synthesis of 3-acyl imidazo[1,5- a ]pyridines. Herein, a novel and efficient Cu(I)-catalyzed three-component annulation method for the synthesis of valuable 3-acyl imidazo[1,5- a ]pyridines by the reaction of 2-pyridinyl-substituted p -QMs, terminal alkynes, and TsN 3 in the presence of O 2 under mild conditions have successfully been developed. The investigation indicated that molecular oxygen (O 2 ) and TsN 3 , respectively, serving as oxygen and nitrogen sources, were essential for the successful completion of the reaction system.