Unexpected intramolecular cyclization of some 2′-aminochalcones to indolin-3-ones mediated by Amberlyst®-15

The intramolecular cyclization of 2'-aminochalcones derived from 2- and 4-Pyridinecarboxaldehydes was carried out in the presence of Amberlyst (R)-15/AcOH media. Unexpectedly, the reaction Proceeded through a 5-exo process turning into an alternative approach for the synthesis of 2-(pyridinylmethylene)indolin-3-ones. (c) 2008 Published by Elsevier Ltd.