A new CAN-catalyzed domino process related to the Nenitzescu reaction: very concise access to fused ortho-indolequinones from simple precursors

The CAN-catalyzed three-component reaction between primary amines, β-ketoesters and naphthoquinone in ethanol at room temperature afforded as the main products the corresponding Michael adducts, oxidized to the quinone stage. When these compounds were refluxed in ethanol in the presence of CAN, they afforded tricyclic ortho-quinones derived from the benzo[g]indole-4,5-dione framework via a domino mechanism comprising a sequence of 5-exo-trig cyclization, elimination, Michael addition, oxo–enol tautomerism and hydroquinone oxidation individual steps.