Direct Synthesis of 2-Alkynylindolin-3-ones via Copper-Catalyzed Reductive Alkynylation of 2-Arylisatogens

2-Alkynylindolin-3-ones (pseudoindoxyl derivatives) are accessed directly from 2-arylisatogens through a CuTC-catalyzed reductive alkynylation with terminal alkynes. The transformation proceeds in a one-step cascade, combining alkyne addition at the 2-position of the isatogen nucleus with concurrent N-O bond cleavage to deliver 2-alkynylindolin-3-ones in yields of up to 89% under relatively mild thermal conditions. The method displays a broad substrate scope and operational simplicity, highlighting its value as a practical entry to this class of heterocycles. Control experiments further reveal a redox interplay of copper species, sustained by molecular oxygen, which underpins the tandem alkyne addition and N-O bond reduction events.