O -Heterocycles-Fused Indoles via Tandem 1,2-Indole Migration–Hydroxycyclization Reactions in 2-Hydroxyalkyl-3-propargylindoles

Gold(I)-catalyzed tandem cyclization reactions of 3-propargylindoles bearing a hydroxyalkyl substituent at C2 enable rapid access to indole-fused cyclic ethers through the vinylogous reactivity of α,β-unsaturated gold-carbene intermediates. A selective intramolecular Michael-type attack of the hydroxyl group, supported by DFT studies, affords indole-fused six-, seven-, and eight-membered O-heterocycles under mild conditions. A one-pot hydrogen transfer process further delivers reduced pyranoindoles, highlighting the versatility and synthetic potential of this method.