Chemodivergent Synthesis of Indole Derivatives: [2 + 3]-Annulation of Oxindole-Derived MBH Carbonates with α-Enolic Dithioesters and Subsequent Branching Transformations

A chemodivergent synthetic strategy for constructing a series of structurally diverse indole derivatives has been developed, utilizing oxindole-derived Morita-Baylis-Hillman (MBH) carbonates and α-enolic dithioesters as key building blocks. By leveraging the unique reactivity of both components, including the multisite reactivity of α-enolic dithioesters and the versatile reaction potential of oxindole-based MBH derivatives, the reaction proceeds via an initial [2 + 3] annulation to afford polysubstituted thiophene scaffolds tethered with an oxindole motif. This common annulation intermediate undergoes branching transformations under tailored reaction conditions: lactam-enolization-mediated trapping delivers hydrothiophene-tethered indoles, whereas base-promoted skeletal rearrangement furnishes two classes of spirooxindole derivatives spirofused with cyclopentadienes or thiopyrans.