A facile method for the synthesis of 3-substituted 3-(Alkylthio)oxindoles or 3-alkoxyoxindoles

We report a highly efficient perchloric acid catalyzed substitution reaction of 3-hydroxyoxindoles with thiols and alcohols for the synthesis of 3-substituted 3-(alkylthio)oxindoles or 3-alkoxyoxindoles, with catalyst loading down to 0.5 mol%. The scope and limitation of this method has been studied. An unprecedented mercury(II) perchlorate trihydrate catalyzed tandem Sakurai-Hosomi/(thio)ether formation reaction, starting from isatins, allyltrimethylsilane, and thiols or alcohols, has also been developed, which enables the facile synthesis of versatile 3-(alkylthio)- or 3-alkoxy-3- allyloxindoles.