Rapid Oxidation Indoles into 2‐Oxindoles Mediated by PIFA in Combination with <i>n</i>‐Bu₄NCl ⋅ H₂O

Abstract

Abstract We report the development of a rapid approach for directly converting indoles into 2‐oxindoles promoted by HOCl formed in situ from the combination of (bis(trifluoroacetoxy) iodo)benzene (PIFA) and n ‐Bu 4 NCl ⋅ H 2 O. The procedure is widely functional group tolerant and provides 2‐oxindoles in up to 95% yield within 5 min. The potential applications of the developed methodology are demonstrated by the gram‐scale preparation of 3‐methyl‐2‐oxindole ( 11 a ), the one‐pot two‐step syntheses of spiro‐oxindoles 26 a and 26 b , and the formal synthesis of (‐)‐folicanthine ( 2 ). magnified image