Enantioselective Epoxidation of Alkenes by Jacobsen Catalyst Anchored onto Aminopropyl-functionalised Laponite, MCM-41 and FSM-16

The Jacobsen catalyst derivative, (R,R)-[Mn(3,5-dtButsalhd)]ClO4-CAT 2, was immobilized through axial coordination of the metal center onto a Laponite, MCM-41 and FSM-16 functionalized with 3-aminopropyltriethoxysilane. The catalytic activity of the Mn-based materials was screened for the enantioselective epoxidation of three olefins: styrene, alpha-methylstyrene and 6-CN-2,2'-dimethychromene, using m-CPBA/NMO as oxidant, and the results were compared with the corresponding homogenous complex (CAT 2) and with the Jacobsen's catalyst, (R,R)-[Mn(3,5-dtButsalhd)Cl]-CAT 1. The results indicate that under comparable condition, the Laponite-based materials show both, higher epoxide yield and enantiomeric excess (ee%) compared to MCM-41 and FSM-16-based materials. The best ee% value was obtained for the substrate 6-CN-2,2'-dimethylchromene (64%) which is very close to that obtained with CAT 2 (67%) in homogeneous phase; for the two regular mesoporous materials (MCM-41 and FSM-16) the catalytic results were more favorable for the FSM-16 samples.