Copper(II)−Bis(oxazoline) Catalyzed Asymmetric Diels−Alder Reaction with α′-Arylsulfonyl Enones as Dienophiles

α′-Arylsulfonyl enones are efficient bidentate dienophiles for the Cu(II)-bis(oxazoline) catalyzed enantioselective Diels−Alder reaction with a number of dienes, affording the corresponding products with good to high enantiomeric excesses. The resulting products can be alkylated and the sulfone removed, so α′-arylsulfonyl enones can be regarded as surrogates of simple monodentate enones, which are poor dienophiles with this catalytic system.