Abstract Cu (I) Cl-catalyzed oxidation of indole 1 by dioxygen in anhydrous acetonitrile leads to highly reactive 3-oxo 3H-indole 2, which provides directly 2-dialkylamino 3-oxo 3H- indoles 3 in presence of dialkylamines. Amidines 3, previously difficult to prepare, are potentially useful synthons in the field of heterocyclic chemistry.