Hydroarylation of Alkenes by protonation/Friedel-Crafts Trapping – HFIP-Mediated Access to Per-Aryl Quaternary Stereocentres

Upon treatment with a combination of HFIP and a strong Brønsted acid, alkenes behave as Brønsted bases and protonate to give carbocations which can be trapped by electron rich arenes. The reaction constitutes a Friedel-Crafts (FC) hydroarylation which proceeds with Markovnikov selectivity and is orthogonal to traditional metal catalyzed processes. The products contain polyarylated quaternary carbon atoms which are difficult to obtain via alternative methods. Intermolecular transfer hydrogenation and hydrothiolation are also demonstrated.