Direct Synthesis of 2-Alkynylindolin-3-ones via Copper-Catalyzed Reductive Alkynylation of 2-Arylisatogens
Kunlayanee Punjajom1, Kooljira Koekon1, Piyaporn Arunkirirote2
1Program in Chemical Sciences, Chulabhorn Graduate Institute, Center of Excellence on Environmental Health and Toxicology (EHT), Office of Permanent Secretary (OPS), Ministry of Higher Education, Science, Research and Innovation (MHESI), 54 Kamphaeng Phet 6, Laksi, Bangkok 10210, Thailand.
Abstract:
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.
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