Chiral Ir(I) complex supported on external surface passivated SBA-15 as heterogeneous catalyst for asymmetric transfer hydrogenation of aromatic ketones

• External surface passivated SBA-15 was applied to support chiral Ir(I) catalyst.
• Notably higher ee values than the homogeneous catalyst were obtained.
• Passivated support was better than the nonpassivated material.
• Passivated SBA-15 based catalyst could be easily recycled.

Chiral 9-amino epi-cinchonine was anchored on external surface passivated SBA-15 as well as calcined SBA-15. The two resulting materials were used as catalysts for the asymmetric transfer hydrogenation of aromatic ketones after complexing with [Ir(COD)Cl]2. Higher enantioselectivities were obtained over the passivated SBA-15 supported catalyst compared with the catalyst based on calcined SBA-15 as well as the homogeneous counterpart. Especially for the substrate of acetophenone, an obviously high enantiomeric excess (ee) of 74% (homogeneous ee: 60%) was achieved with comparable conversion to the homogeneous catalyst (97% vs. 98%). Furthermore, the passivated SBA-15 supported catalyst demonstrated higher stability during the asymmetric transfer hydrogenation reaction as compared with the catalyst based on calcined SBA-15.

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