Supported zirconium-based continuous-flow microreactor for effective Meerwein–Ponndorf–Verley reduction of cyclohexanone

• New continuous-flow monolithic microreactor for MPV reduction was proposed.
• Activity of different zirconium species incorporated onto silica was compared.
• Catalyst stability was confirmed during long-time experiments in microreactor.

Continuous-flow monolithic silica microreactor activated with anchored isolated zirconium species was shown to be a very convenient and efficient system for chemoselective Meerwein–Ponndorf–Verley reduction. It was shown that isolated Zr4 + ions covalently bonded to the silica surface and terminated with isopropoxy/hydroxo ligands can be much more catalytically active than supported zirconia. Conversion of cyclohexanone approached 100% and excellent catalytic selectivity and stability were obtained in 8 cm long microreactor during 8 catalytic cycles. The microreactors also enable better control of undesired hydrolysis of highly reactive metal precursors during functionalisation of the monoliths.

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