AlCl3-Catalyzed Intramolecular Hydroarylation of Arenes with Alkynes

Herein, we wish to report the main-group metal Lewis acid catalyzed intramolecular hydroarylation of arenes with alkynes. This cyclization proceeds efficiently in the presence of a catalytic amount of AlCl3, affording phenanthrenes in moderate to excellent yields. The catalyst is cheap and nontoxic. The functional-group tolerance is high. A plausible electrophilic aromatic substitution reaction mechanism is proposed for this transformation.