3-Aminooxindoles via Microwave-Assisted Intramolecular Arylation

Significance

Reported here is the microwave-assisted intramolecular Pd-catalyzed arylation of enolates of substituted amino acids to give quaternary 3-aminooxindole derivatives. Initial experiments following Hartwig’s conditions (J. Org. Chem. 1998, 63, 6546) in dioxane or toluene using conventional heating resulted in low yields (10-12%) of products. Under microwave conditions, efficiency and generality in terms of substrate scope for the enolate substituents (R^²-R⁴) including cyclic and acyclic dialkylamines was demonstrated. However, phenyl-ring substitution was not studied. The indolo-fused benzodiazepinone A, the result of direct intramolecular C2-indole arylation, provides a new and simple entry into this heterocyclic ring system.