Immobilization of chiral amino alcohol (S)-2-amino-4-methylpentan-1-ol on MCM-41 nanoporous silica and its applications in asymmetric allylic C-H bond oxidation of cycloalkenes

There are several methods for the preparation of pure enantiomeric compounds which one of them is the use of chiral catalysts in asymmetric synthesis. For this purpose, we used a heterogeneous chiral catalyst because its separation and recycling is more convenient than homogeneous catalyst.1, 2 The allylic oxidation of olefins using peresters in the presence of copper catalyst to give allylic esters is known as the Kharash-Sosnovsky reaction. This reaction has been the subject of great interest over the last decade and provides access to chiral allylic alcohols, which are key intermediates in natural product synthesis. 2 In this study, MCM-41 was prepared and modified by (3-chloropropyl) trimethoxy silane. Afterward, the chiral amino alcohol (S)-2-amino-4-methyl pentan-1-ol which is synthesized by reduction of corresponding chiral amino acid L-leucine, immobilized on Cl-MCM-41 mesoporous silica. The synthesized chiral heterogeneous ligand with copper salt was used in the asymmetric allylic C-H bond oxidation of cycloalkenes under different conditions. The chiral allylic esters were achieved in high yields and moderate enantioselectivities. 2 a,c

کلیدواژه ها:

Chiral amino alcohol ، Chiral heterogeneous catalysts ، Chiral allylic ester ، Allylic C-H bond oxidation.