Gold-Catalyzed Dual Annulation of Homopropargyl Alcohols with Nitrones: Synthesis of Tetrahydropyrano[4,3-b]indole Scaffolds

An unprecedented gold-catalyzed dual annulation of homopropargyl alcohols with nitrones has been developed, which provides an effective access to the 1,3,4,5-tetrahydropyrano[4,3-b]indole derivatives in good to high yields. Mechanistically, this one-pot three-step cascade reaction is initiated by a gold-catalyzed alkyne oxoarylation, followed by an intramolecular cyclodehydration and terminated with an intermolecular cyclization with aldehyde which is a leaving species in the early stage of this cascade process.