Lewis Acid-Catalyzed Cascade Dehydrative Annulation: Divergent Synthesis of Bi- and Tricyclic Frameworks From 2-Arylethanols and Propargylic Alcohols

A Lewis acid-catalyzed cascade reaction to carbazole, naphthalene, tetrahydropyrano[4,3- b ]indole, and isochromane frameworks from readily available 2-arylethan-1-ol and propargylic alcohols is described. A plausible reaction pathway is deduced from the identification and structural analysis of a key intermediate. Furthermore, the scalability of this protocol was demonstrated through a gram-scale synthesis.