Immobilization of the amino acid (L)-valine and amino alcohol (L)-valinol on SBA-15 nanoporous silica and investigation of their potential in asymmetric allylic oxidation of alkenes

Immobilization of chiral ligands onto mesoporous silica such SBA-15, SBA-16, MCM-4, and MCM-41 for the preparation of chiral heterogeneous catalysts have attracted enormous interest in asymmetric synthesis1, 2. Chiral allylic esters that are one of the important intermediates in the pharmaceutical industry were prepared via asymmetric allylic C-H bond oxidation of cycloalkenes with perester in the presence of copper salt (Kharasch–Sosnovsky reaction) 3.In this study, we prepared mesoporous silica SBA-15 and modified by 3-chloropropyl trimethoxy silane. Afterward, amino acid L-Valine and amino alcohol L-Valinol that is synthesized by reduction of corresponding amino acid L-Valine, immobilized on modified SBA-15. The synthesized heterogeneous chiral catalysts were characterized by using FT-IR, XRD, SEM, EDX, TGA and BET-BJH techniques. The copper complexes of these chiral heterogeneous catalysts were investigated in the asymmetric allylic C-H bond oxidation of cycloolefins. The chiral allylic esters were obtained in high yields and moderate enantioselectivities under the best condition 3

Keywords:

Amino acid , Amino alcohol , Chiral heterogeneous catalyst , Chiral allylic ester , SBA-15.