Asymmetric Epoxidation Of Α-methylstyrene Research Articles

Enantioselective epoxidation of nonfunctionalized alkenes catalyzed by recyclable new homochiral bis-diamine-bridged bi-Mn(salen) complexes

Three new homochiral bis-diamine-bridged bi-Mn(salen) complexes were synthesized. Their catalysis on asymmetric epoxidation of α-methylstyrene, styrene and indene was studied with NaClO and m-CPBA as oxidants respectively. This homogeneous catalyst exhibited comparable catalytic activity and enantioselectivity to the Jacobsen’s catalyst in the asymmetric epoxidation of unfunctionalized olefins. Furthermore, the catalyst could be conveniently recovered and reused at least five times without significant losses of both activity and enantioselectivity. Specially, it also could be efficiently used in large-scale reactions with superior catalytic disposition being maintained at the same level, which provided the potential for the applications in industry. The effect of axial bases, temperature and solvent on activity and enantioselectivity of the catalytic system were also studied.

Chiral salen Mn(iii) complexes immobilized onto crystalline aluminium oligo-styrenyl phosphonate-hydrogen phosphate (AlSPP) for heterogeneous asymmetric epoxidation

A novel type of organic polymer–inorganic hybrid material layered crystalline aluminium oligo-styrenyl phosphonate-hydrogen phosphate (AlSPP) was designed and prepared in the absence of any template. The chiral salen Mn(III) complex immobilized onto alkoxy-modified AlSPP was synthesized and characterized by FT-IR, diffusion reflection UV-vis, AAS, N2 volumetric adsorption, SEM, TEM, XRD, TG and AFM. The supported catalysts displayed superior catalytic activities in the asymmetric epoxidation of α-methylstyrene and indene with m-CPBA as an oxidant. Delightfully, the heterogeneous catalysts afforded a remarkable increase in conversion and ee values without the expensive O-coordinating axial bases for the asymmetric epoxidation of olefins. The catalysts can be easily recovered and reused with a slight decrease in activity and enantioselectivity after ten cycles. Furthermore, they could also be efficiently used in large-scale reactions with the enantioselectivity being maintained at the same level, which provided the potentiality for application in industry.

Structure-control in assembly of nanosheets: Novel chiral catalysts for the asymmetric epoxidation of α-methylstyrene without axial base

Abstract Heterogeneous chiral catalysts with different structure, surface character and location of active species were assembled by salen Mn(III) complex and α-Zr(HPO4)2 nanosheets. The bumpy edge-accumulated surfaces of nanosheets lead the catalyst to have a high ee value without axial base in the asymmetric epoxidation of α-methylstyrene.

A high efficient large-scale asymmetric epoxidation of unfunctionalized olefins employing a novel type of chiral salen Mn(III) immobilized onto layered crystalline aryldiamine modified zinc poly(styrene-phenylvinylphosphonate)-phosphate

A series of chiral salen Mn(III) catalysts immobilized onto aryldiamine modified ZnPS-PVPA with different ratio of phosphonate/phosphate for asymmetric epoxidation were synthesized and characterized by FT-IR, diffusion reflection UV–Vis, AAS, N2 volumetric adsorption, SEM, TEM, XPS, XRD and TG. The supported catalysts displayed superior catalytic activities in the asymmetric epoxidation of α-methylstyrene and indene with m-CPBA and NaIO4 as oxidants. Moreover, the heterogeneous catalysts were relatively stable and could be recycled nine times in the asymmetric epoxidation of α-methylstyrene. Furthermore, this novel type of catalyst could also be validly used in large-scale reactions with superior catalytic disposition being maintained at the same level, which possessed the potentiality for application in industry.

Catalytic asymmetric epoxidation of unfunctionalized olefins using a series novel type of layered crystalline organic polymer–inorganic hybrid zinc phosphonate–phosphate immobilized aryldiamine modified chiral salen Mn(III) complex

In this report we demonstrate the suitability of layered crystalline organic polymer–inorganic hybrid material ZnPS–PVPA with different content of the organic group and different inorganic phosphate as catalyst supports for asymmetric catalysis. A series of the chiral salen Mn(III) complex immobilized onto ZnPS–PVPA modified by aryldiamine were synthesized and characterized by FT-IR, diffusion reflection UV–vis, AAS, N 2 volumetric adsorption, SEM, TEM, XRD and TG. The supported catalysts displayed superior catalytic activities in the asymmetric epoxidation of α-methylstyrene and indene with m-CPBA and NaIO 4 as oxidants, compared with the corresponding homogeneous catalyst ( ee, >99% vs 54% and >99% vs 65%). And the heterogeneous catalysts are relatively stable and can be recycled nine times in the asymmetric epoxidation of α-methylstyrene. These results revealed that the special structure of ZnPS–PVPA played vital impacts on the conversion and enantioselectivity. Furthermore, this novel type of catalyst can also be validly used in large-scale reactions with superior catalytic disposition being maintained at the same level, which possessed the potentiality for application in industry.

Chiral Salen Mn(III) Complex Axial Coordination Immobilized on Diamine Modified Alspp and Highly Efficient Large-Scale Epoxidation of Olefins as a Recoverable Catalyst

Aluminium oligo-styrenyl phosphonate-hydrogen phosphate (AlSPP) was used as organic–inorganic hybrid support after chloromethylation, and then with using different diamines as a reactive surface modifier. We realized the homogeneous chiral salen Mn(III) complex axially immobilized on modified AlSPP by a covalent grafting method. The prepared heterogeneous salen Mn(III) complexes were characterized by different techniques such as FT-IR, diffusion reflection UV–Vis, AAS, XPS, N2 volumetric adsorption, SEM, TEM and TG. The chiral salen Mn(III) complexes were immobilized onto the AlSPP through axial coordination for the first time with m-CPBA/NMO as an oxidant system for asymmetric epoxidation of unfunctionalized olefins. The supported catalyst showed very good performance in the asymmetric epoxidation of α-methylstyrene and indene. The catalyst could be easily recovered and reused without significant loss of activity and enantioselectivity after nine cycles. This novel heterogeneous catalyst could be efficiently used in large-scale reactions with the enantioselectivity being maintained at the same level, which offer great possibilities for application in industry.