Highly efficient asymmetric epoxidation of olefins with a chiral manganese-porphyrin covalently bound to mesoporous SBA-15: Support effect

- A catalyst was synthesized by immobilization of a chiral MnIII-porphyrin on SBA-15.
- The catalyst was efficient and enantioselective in the aerobic epoxidation of olefins.
- The catalyst showed excellent enantioselectivity than its homogeneous analogue.
- The catalyst oxidized indene to chiral (1 S,2R)-indene oxide (ee 100%).
- The chiral catalyst was recyclable at least five times.

A chiral MnIII-porphyrin complex covalently bonded with mesoporous SBA-15 (SBA15-[Mn(TCPP-R∗)Cl]) was synthesized and fully characterized. The heterogeneous SBA15-[Mn(TCPP-R∗)Cl] exhibited remarkable catalytic activity toward enantioselective olefin epoxidation using O2 as terminal oxidant in the presence of isobutyraldehyde. The catalyst showed higher enantioselectivity than its homogeneous counterpart in the oxidation of α-methylstyrene. SBA15-[Mn(TCPP-R∗)Cl] catalyzed epoxidation of styrene was achieved within 8 h and optically active styrene oxide was obtained in 89% ee and 90% yield. Likewise, styrene derivatives (trans-β-methylstyrene, indene), conjugated cis- and trans-disubstituted olefins (e.g. cis- and tans-stilbene) and terminal olefins were converted effectively to their corresponding epoxides in 63-99% ee under the Mn(III)-catalyzed conditions. The catalyst could be recycled five times without any significant loss in activity.

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