Heterogenization of Chiral Amino Alcohol Ligands by Grafting onto Mesoporous Silica SBA-15 and Their Applications in Asymmetric Allylic C-H Bond Oxidation of Cycloolefins

Enantioselective allylic oxidation of alkenes using organic peresters and copper chiral complexes has been a subject of great interest during the last decade. This reaction provides an access to chiral allylic alcohols which are key intermediates in the synthesis of natural products [1]. Limited natural resources and an increasing demand for enantiomerically pure compounds render catalysis and especially chiral heterogeneous catalysis a key technology and many researchers have taken great interest in these catalysts which is mainly due to the simple filtration and reuse of expensive chiral catalysts and ease of separation [2,3]. In this project, we use (S)-2-amino-2-phenylethanol and (S)-2-amino-3-phenylpropanol which are synthesis by reducing of their corresponding amino acids, as ligands and immobilizing on the modified silica nanoporous SBA-15 [4]. Obtained new heterogeneous ligands characterized by TGA, DTA, XRD, EDX, SEM, and FT-IR. The catalytic potential of these new heterogeneous ligands was applied for the copper catalyzed allylic C-H bond oxidation of cycloolefins. The allylic esters were prepared in good yields and moderate to good enantioselectivities (Scheme1).