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Copper(II)-Catalyzed Domino Synthesis of Indolo[3,2-c]quinolinones via Selective Carbonyl Migration
- Arunprasath, Dhanarajan, Sekar, Govindasamy
- Organic letters 2019 v.21 no.4 pp. 867-871
- acidity, amines, carbenes, catalytic activity, chemical reactions, chemical structure, copper, quinolones, trapping
- A Cu(II)-catalyzed domino process involving the carbene N–H insertion, intramolecular aldol-type trapping and unprecedented ring-expansion of oxindole core through C3-selective 1,2-carbonyl migration is described for the synthesis of indolo[3,2-c]quinolinones. This tetracyclic core, having an all-carbon quaternary center, was efficiently synthesized in high yields from amines and 3-diazo-oxindoles. Mechanistic studies revealed that this reaction proceeds via a stepwise pathway and the involvement of the synergistic catalysis between Lewis acidic copper and hidden Brønsted acidity of in-situ-formed TfOH traces.