Highly Enantioselective Addition Of Organic Zinc Reagents To Aldehydes Catalyzed By C₂ Unsymmetrical Vicinal Diamines

In this dissertation, the high optically active C₂ unsymmetric vicinal dimmines were synthesized through the SmI₂-mediated cross-coupling reaction between chiral N-tert-butylsulfinyl amines and nitrones and used as chiral ligands in the asymmetric addition of aryl zinc reagent or diethylzinc to aldehydes.The chiral N-tert-butylsulfinyl imines and nitrones were synthesized and then they were cross coupled mediated by SmI₂. The C₂ unsymmetric vicinal dimmines were obtained in high ee values. We attempted to enlarge the reaction' scale and found when the product was synthesized on a gram-scale, the enantioselectivity was maintained. So these chial reagents were easy to accumulate.The phenyl zinc reagent was prepared through the reaction of phenylboronic acid and diethylzinc. Catalyzed by the C₂ unsymmetric vicinal dimmines, the phenyl were asymmetrically transferring to aldehydes. We changed the dimmine's structure and found, after comparation, the dimmine which didn't have the hydroxyl function made the most high enantioselectivity for the raction. All of the diaryl methanols' ee values were higher than 92% and the highest ones were up to 99%. We also found that many other aryl zinc reagents addition to phenylaldehyde had excellent enantioselectivity (higher than 92%) too. We investigated the reationship between the ee value of the chiral ligand and that of the product and found it was linear. This suggested that the addition of aryl zinc reagents to aldehydes might be catalyzed by a dimmine catalyst. The chiral sulfinyl amine in the ligand played an important role in the reaction. When it was taken off or converted into orther substitutes, the enantioselectivities dropped obviously in catalyzing the same reaction.The dimmine was also used in the asymmetric addition of diethylzinc to arylaldehydes. Excellent results were found. All the products' ee values were higher than 97%.The dimmine having the hydroxyl function appeared low enantioselectivity (only 31%) in catalyzing the addition of phenylzinc reagent to aldehydes. But when it was used in the asymmetric addition of diethylzinc to arylaldehydes, though the reaction speed was much slower, all the enantioselectivities were found from 80% to 94%.