Synthesis of α-Hydroxy Ketones by Using Magnetic Nanobead Copper Catalysts

Significance

Organic-inorganic hybrid polymer-encapsulated magnetic nanobeads (HP-MB) catalyst was prepared for use as a magnetically separable heterogeneous oxidation catalyst. Commercially available amino-functionalized magnetic beads 1 were mixed with Cu(BF₄)₂×6H₂O and 4,4′-bipyridine (bpy) to form the Cu-bpy HP-MB 2 (eq. 1). The oxidation of various silyl enolates 3a-i with oxygen took place in the presence of 6 mol% of catalyst 2 to give the corresponding α-hydroxy ketones 4a-i in 75-99% yield (eq. 2). This catalyst was separated from the reaction mixture with an external magnet, and reused five times in the oxidation of 3j with no significant loss of activity (eq. 3).