Study On Immobilization Of Catalyst For Epoxidation Of Alkenes

The two heterogenization methods of the manganese catalysts for alkene epoxidations were investigated in this thesis,including the polymerization of Mn Salon complex linked through triazole and the immobilization of the ionic Mn porphyrin in the ionic liquid.Firstly,based on the concept 'Click Chemistry',we designed and synthesized a new poly-Salen ligand linked through triazole.The starting materials of 2-Hydroxy-4-prop-2-ynyloxy-benzaldehyde and 1,3-Diazido-propane reacted efficiently to form bis-salicylaldehyde compound with ditriazole linker unit.Then,the obtained bis-salicylaldehyde was treated with defferent diamines to afford four kinds of polymerized Salen ligands linked through triazole.Mn(â…¢)ion was successfully loaded on these poly-salen ligands by mixing with Mn(OAc)₂ to give the corresponding Mn(â…¢)complexes,which served as the solid catalysts for styrene epoxidations by iodosylbenzene(PhIO)as oxidant with good activity and epoxide selectivity.Furthermore,the developed solid Mn-Salen catalysts could be recovered and reused at least for three times without the obvious loss in activity.The generality of the catalyst for other chained and cyclic alkenes also gave good results.Secondly,an ionic manganese porphyrin(C),with tartrate as the counter anion,was synthesized and applied as a catalyst for styrene epoxidation by PhIO oxidant.In consideration of ionophilicity and compatibility,the pyridinium based ionic liquid(IL) of 1-butyl-pyridinium tetrafluoroborate([Bpy]BF₄)was used as the solvent to immobilize the catalyst C.The developed C-[Bpy]BF₄ IL system exhibited high activity/epoxide selectivity without the involvement of exogenous axial ligands.The following factors contributed to the improved activity and stability of C,including:(1) the use of tartrate anions acting as the stoichiometrical axial ligands;(2)the introduction of the electron-withdrawing pyridinium cations at meso-positions of the the porphyrino ring leading to the reduced electronic-density in C;(3)The effective inhibition ofÏ€-Ï€aggregation of the porphyrin itself by using[Bpy]BF₄ as the solvent. The generality of C-[Bpy]BF₄ to the different styrene derivatives also gave out the good results with good epoxide selectivity and well maintained stereochemistry.