Ring Synthesis of Oxindoles

The main synthesis of oxindoles is simple and direct and involves an intramolecular Friedel-Crafts alkylation reaction as the cyclising step. Also straightforward in concept is the displacement of halogen from an ort/to-halo-nitroarene with malonate, this leading to an oxindole after decarboxylation and reduction of the nitro group with spontaneous lactamisation.  

An alternative route to oxindoles depends on the intramolecular insertion of a rhodium carbenoid, derived from a 2-diazo-l,3-ketoamide, into an adjacent aromatic C-H bond.  

Oxindoles can also be prepared by palladium-catalysed enolate cyclisation of orl/to-halo-anilides.  

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