Synthesis of new chiral imidazolidine disulfides derived from l-cystine and their application in the enantioselective addition of diethylzinc to aldehydes

Several chiral imidazolidine disulfides 4a–d derived from l-cystine have been synthesized. These ligands have been applied as chiral catalysts in the asymmetric addition of diethylzinc to aldehydes. The best results were obtained by employing 5 mol% of imidazolidine disulfide 4a, and chiral secondary alcohols were obtained in up to 91% e.e.