Enantioselective Addition of Thiols to ortho -Quinone Methides Catalyzed by Chiral Phosphoric Acids

The first Bronsted acid catalyzed enantioselective addition of thiols to the in situ generated ortho -quinone methides ( o -QMs) is described. Complementary to the chiral amine catalyzed approach, the present reaction employs a chiral phosphoric acid as the catalyst. The readily available o -hydroxybenzyl alcohols serve as the atom-economical precursors of o -QMs to react with tritylthiol with moderate to good efficiency and enantioselectivity under mild conditions.