Sc(OTf)₃-Catalyzed Synthesis of Indoles and SnCl₄-Mediated Regioselective Hydrochlorination of 5-(Arylamino)pent-3-yn-2-ones

Highly substituted indole derivatives bearing alkyl and aryl moieties can be prepared by Sc(OTf)₃-catalyzed Friedel–Crafts alkenylation of 5-(arylamino)pent-3-yn-2-ones. In addition, a method for regioselective hydrochlorination of 5-(arylamino)pent-3-yn-2-ones mediated by SnCl₄ in moderate to good yields (up to 84%) has been developed. The resulting exclusive Z-selectivity of the C–Cl bond can be further exploited using cross C–N coupling reactions.