A study of enantioselective syntheses by Sharpless asymmetric oxidation for aryl sulfoxides containing oxygen groups at the ortho position

While ortho-alkoxy aryl sulfoxides including various substituents were synthesized by Sharpless asymmetric oxidation reaction, we optimized the reaction conditions and screened better combination of starting materials to obtain high enantioselectivity. The result suggested new information that electron-withdrawing substituents on the aromatic ring have a strong influence upon enantioselectivity of the products. Also, several chiral ligands for Sharpless asymmetric oxidation reaction were evaluated to improve the enantioselectivity. High enantioselectivity of ortho-alkoxy aryl chiral sulfoxides have been achieved by Sharpless oxidation reaction using Ti(O-i-Pr)4 and diethyl tartrate under anhydrous condition. In particular, the enantioselctivity of products was influenced by electron-withdrawing substituents on the aromatic ring, such as nitro, ester and aldehyde groups.