Controllable synthesis of 3-chloro- and 3,3-dichloro-2-oxindoles hypervalent iodine-mediated chlorooxidation

An efficient and controllable protocol for the synthesis of 3-chloro- and 3,3-dichloro-2-oxindoles has been developed via hypervalent iodine-promoted chlorooxidation. By using two equivalents of 1-chloro-1,2-benziodoxol-3-(1 H )-one, a wide range of indoles were transformed into 3-chloro-2-oxindoles in DMF/CF 3 CO 2 H/H 2 O at room temperature with good yields. As far as we know, this is the first report on the selective C-2 oxidation and C-3 monochlorination of simple indoles. In addition, three equivalents of the same hypervalent iodine afforded 3,3-dichloro-2-oxindoles in up to 99% yields under optimized conditions (dioxane/H 2 O, 80 °C). The method features mild reaction conditions, the widespread availability of the substrates, and good functional group tolerance. Controllable synthesis of 3-chloro- and 3,3-dichloro-2-oxindoles via chlorooxidation of indoles has been developed in up to 99% yields.