Non-covalent immobilization of chiral copper complexes on Al-MCM41: Effect of the nature of the ligand

• Chiral box- and azabox-Cu complex were non-covalently immobilized on Al-MCM41.
• Cu(OTf)2 was first impregnated by incipient wetness and then treated at 450 °C.
• Final modification with box and azabox leads to stable immobilized complexes.
• Azabox-Cu complexes were more stable upon recycling up to 5 times.

Cu-Al-MCM41, prepared by deposition of copper(II) triflate with incipient wetness impregnation and thermal treatment under air flow, can be modified with different chiral ligands of the bis(oxazoline) family. The efficiency of the supported chiral catalysts in the enantioselective cyclopropanation of styrenes with ethyl diazoacetate depends on the nature of the ligand. The azabis(oxazolines) perform much better than the bis(oxazolines) and give stable catalysts that can be used for at least five consecutive runs, with productivities that can reach values close to 1000 molecules of cyclopropane per copper site. The best enantioselectivities obtained with these catalysts are in the range of 60–70% ee in the reaction at 90 °C.

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