|
چکیده
|
Asymmetric allylic C-H bond oxidation of olefins to chiral esters is one of the most important reactions in organic chemistry, that unlike the hydroxylation and epoxidation, the second functional group forms while double bond remains unchanged. Several efficient and enantioselective strategies for synthesis of chiral products by using chiral homogeneous and heterogeneous catalysts have been developed. In other hand heterogeneous catalysts have some advantages such as easy separation and recovery, reducing metal productions pollution, easy usage and better control of the process. According to the mentioned reasons, we became interested in the immobilization of chiral amino acid ligands on nanoporous silica SBA-15. The resulting heterogeneous catalysts were characterized by TGA, DTA, XRD, EDX, SEM and FT-IR. After that the chiral copper (II) complexes of these chiral supported heterogeneous catalysts were utilized in direct asymmetric allylic C-H bond oxidation of cyclohexene. The chiral allylic esters were achieved in good yields and good enantiomeric excesses . The catalysts were recovered and reused for at least five reaction cycles without significant change in their nanostructures as evidenced by surface analysis.
|