Oxidative Dearomatization of Indoles via Pd-Catalyzed C–H Oxygenation: An Entry to C2-Quaternary Indolin-3-ones

An oxidative dearomatization chemistry of 2-arylindole via a unique pathway involving Pd-catalyzed C–H peroxygenation is documented. Coupled with cascade transformation, it provides a new route to access indolin-3-ones bearing a C2-quaternary functionality, including a chiral center (indoxyls), a motif prevalent in indole alkaloids but synthetically underexplored. The method is chemo- and regioselective and compatible with versatile substrates. A mechanism has been outlined on the basis of results of control experiments, isolation/use of intermediates, and spectroscopic studies.