Copper-Catalyzed Domino Annulation of Isoselenocyanates: A Pathway to Structurally Diverse <i>N</i>, Se-Bis-Heterocyclic, and Fused Heterocyclic Compounds

A copper-catalyzed domino addition/cyclization reaction was developed to synthesize novel benzoselenazole-linked 1,2,3-triazole and tetracyclic fused 12<i>H</i>-benzo[4,5]selenazole[2,3-<i>b</i>]quinazolin-12-one derivatives from isoselenocyanates. This domino reaction efficiently constructed multiple new chemical bonds in a single step, forming either four (one C-Se and three C-<i>N</i>) or three (one C-Se and two C-<i>N</i>) bonds. The reaction offers several key advantages, including mild conditions, broad substrate compatibility, and straightforward and safe operation. It presents a new method for synthesizing <i>N</i>, Se-containing polycyclic compounds, which have potential interest in medicinal chemistry. Notably, some of the synthesized compounds exhibited anticancer activity with IC₅₀ values below 20 μmol L^-1 against T24 human bladder cancer cells.