A highly efficient In(OTf)3-catalyzed [3+3] annulation of spirocyclopropyl oxindoles with 1,4-di-thiane-2,5-diol

Abstract Spirooxindoles play an important role in drug discovery and development. The development of efficient methods for the synthesis of spirooxindoles from easily available starting materials is of current interest. Herein, we report in detail the In(OTf)3-catalyzed [3 + 3] annulation of spirocyclopropyl oxindoles and 1,4-di-thiane-2,5-diol, which allows the facile preparation of spiro[indoline-3,4'-thiopyran]-2-ones bearing (tetrahydro)thiopyran skeleton.