Synthesis of GO-SalenMn and Asymmetric Catalytic Olefin Epoxidation

Abstract

Graphene oxide (GO) was used as a catalyst carrier, and after the hydroxyl group in GO was modified by 3-aminopropyltrimethoxysilane (MPTMS), axial coordination and immobilization with homogeneous chiral salenMnCl catalyst were carried out. The immobilized catalysts were characterized in detail by FT–IR, TG–DSC, XPS, EDS, SEM, X-ray, and AAS, and the successful preparation of GO-salenMn was confirmed. Subsequently, the catalytic performance of GO-salenMn for asymmetric epoxidation of α-methyl-styrene, styrene, and indene was examined, and it was observed that GO-salenMn could efficiently catalyze the epoxidation of olefins under an m-CPBA/NMO oxidation system. In addition, α-methyl-styrene was used as a substrate to investigate the recycling performance of GO-salenMn. After repeated use for three times, the catalytic activity and enantioselectivity did not significantly change, and the conversion was still greater than 99%. As the number of cycles increased, the enantioselectivity and chemoselectivity gradually decreased, but even after 10 cycles, the enantiomeric excess was 52%, which was higher than that of the homogeneous counterpart under the same conditions. However, compared to fresh catalysts, the yield decreased from 96.9 to 55.6%.

Chiral Graphene Hybrid Materials: Structures, Properties, and Chiral Applications

“…1) Chiral Mn complex is first prepared and then immobilized onto modified graphene. [ 197–200 ] 2) Mn complex is first prepared and then immobilized on premodified graphene, followed by introducing chiral components directly combined with the metal complex. [ 195 ] 3) Mn complex is first prepared and immobilized on premodified graphene; then chiral components are introduced onto graphene.…”

“…Graphene provides an excellent platform for creating new catalysts due to its 2D architecture and unique electrochemical properties. Among the chiral building blocks for constructing graphene based chiral material systems summarized in Section 2, proline, [ 41,43,53,58 ] enzymes, [ 145 ] and metal complexes [ 195–200,202,205–208 ] have become the most extensively used chiral species for developing chiral hybrid catalysts. To better address the issues, at this point, organocatalysis should be remarked first.…”

“…[ 58 ] Relative to proline, chiral metal complexes offer more possibilities. They can be adopted to perform a wider range of asymmetric reactions, e.g., olefin oxidation (with Mn complex), [ 195 ] olefin epoxidation (Mn complex), [ 196–200 ] sulfoxidation (Ti complex), [ 202 ] hydrogenation (Rh complex, [ 205 ] Ni complex, [ 207 ] and Pd complex [ 208 ] ), and ketone transfer hydrogenation (Ru complex). [ 206 ] The metal complex catalysts and the corresponding asymmetric reactions are summarized in Table 6.…”

Editorial: Special Issue on “Advanced Strategies for Catalyst Design”

“…The problem of asymmetric olefin epoxidation has been investigated and thoroughly discussed by Zou et al [2], who employed salenMn immobilized on graphene oxide as catalyst. In this Special Issue, 11 contributions dealing with different problems of catalysis are gathered, and the main topics are summarized here.…”

“…The problem of asymmetric olefin epoxidation has been investigated and thoroughly discussed by Zou et al [2], who employed salenMn immobilized on graphene oxide as catalyst.…”