Rapid Oxidation Indoles into 2‐Oxindoles Mediated by PIFA in Combination with n‐Bu4NCl ⋅ H2O.

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‐Bu4NCl ⋅ H2O. 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). [ABSTRACT FROM AUTHOR]