In the presence of tetrabutylammonium fluoride and molecular sieves (MS) 4 Å in DMF, an efficient autoxidation reaction of 2‐oxindoles with ketones under air at room temperature has been developed. This approach may provide a green, practical, and metal‐free protocol for a wide range of biologically important 3‐hydroxy‐3‐(2‐oxo‐alkyl)‐2‐oxindoles.