A catalytic enantioselective approach for the formation of chiral CO2-synthons is presented. The described methodology is based on the reaction of dienes with diethyl ketomalonate using C 2-symmetric bisoxazolines as the chiral ligands and copper (II) and zinc (II) as the Lewis acids. For cyclic dienes the reaction proceeds in good yield and with up to 93% ee for 1, 3-cyclohexadiene, while for cyclopentadiene the reaction also proceeds well at low ...