Copper-catalyzed enantioselective esterification of allylic C-H bonds of olefins in the presence of heterogeneous oxazoline base ligands with aromatic substituents

Asymmetric catalysis with chiral complexes has received considerable attention in recent years, and its contribution to the art of organic synthesis has become of leading importance. The ideal ligand, in principle, should offer the user a series of advantages: it has to be easily prepared, cheap and stable. It should also give very selective and flexible catalysts. Lately, oxazoline-based chiral ligands are considered as qualified catalysts by many of chemists.1 The enantioselective allylic oxidation of olefins in the presence of copper catalysts is a topic of great interest and the reaction can be run using peresters to synthesize allylic esters (Kharasch-Sosnovsky reaction).2,3 In this work, we prepared mesoporous silica MCM-41 and then functionalized by 3-chloro propyl trimethoxy silane. The synthesized chiral oxazoline ligands such as (S)-4-phenyl-4,5-dihydroxazole-2-amine and (S)-4-benzyl-4,5-dihydroxazole-2-amine immobilized on modified MCM-41. After that, we used the obtained chiral heterogeneous ligands in asymmetric allylic oxidation of alkenes.4

کلیدواژه ها:

Allylic C-H bonds oxidation ، Heterogeneous oxazoline base ligand ، Chiral allylic ester.