A metal-free route for the preparation of 2-monosubstituted indolin-3-ones, including 2-alkoxyindolin-3-ones and 2-acyloxyindolin-3-ones from commercially available indoles, has been developed employing (bis(trifluoroacetoxy)iodo)benzene (PIFA) as an oxidant. The present protocol features mild reaction conditions, good tolerance with diverse functional groups, and a wide substrate scope, affording the desired products in good yields. This transformation is easy to scale up, and the desired products can be further modified. Most importantly, this method is suitable for the late-stage modification of bioactive molecules. Mechanism studies show that this transformation involves metal-free radical dearomatization and oxygenation. Furthermore, this method also provides a practical and efficient way to prepare indolin-3-ones from commercially available reagents in one step.