First catalytic enantioselective version of a thia hetero-Diels–Alder reaction with dithioesters

The first example of a catalytic asymmetric thia hetero-Diels–Alder reaction, in which a chiral Lewis acid activates the thiocarbonyl dienophile, is described. The reactions catalyzed by copper(II)-bis(oxazolines) complexes of three dithioesters with simple dienes (such as cyclopentadiene or 2,3-dimethyl-1,3-butadiene) afford optically active dihydrothiopyrans with ees up to 82%. Some aspects of the reaction were investigated by computational means.