Copper-Catalyzed\nThree-Component Tandem Cyclization\nfor One-Pot Synthesis of Indole-Benzofuran Bis-Heterocycles

A one-pot, three-component synthesis of indole-benzofuran\nbis-heterocycles\nfrom terminal alkynes, salicylaldehydes, and indoles has been developed\nvia copper-catalyzed tandem annulation. This catalytic system utilizes\nreadily available starting materials, enabling predictable synthesis\nof indole-benzofuran bis-heterocycles with broad substrate versatility,\nexcellent regiocontrol, and gram-scale amenability. The reaction proceeds\nvia a sequential pathway involving A3 coupling, 1,4-conjugate addition,\nand 5-<i>exo</i>-<i>dig</i> cyclization.