Ab ifunctional heterogeneous catalystb ased on the easily produced and economic NiGa layered double hydroxide hasb een developed for the aerobic oxidation/ condensation tandem reactions between aromatic alcohols and active methylene compounds. Good tolerance for varied alcohols and nucleophiles has been observed. Control experiments verified the bifunctional role in the tandem reaction. The protocol could open up new perspectives in the rational design of efficient bifunctional catalytic systems.Ta ndemr eactions have attracted significant attentionb ased on their improved overall process efficiency and reduced production wastes. [1] Designing multifunctional catalysts with spatially isolated multiple active sites is essentialf or progressing multistep reaction cascades. Generally,i ti sm ore easier for heterogeneousc atalysts than for homogeneous ones to incorporate differentc atalytic sites in one system. [2] a,b-Unsaturated aromatic dicyanides are very important intermediates in the design and synthesis of suitable drug molecules.S ome heterogeneous catalysts, such as Pd-nanoparticle-supported Nano-ZSM-5, [3] Pd/LS-AT-OH À catalyst, [4] Pd 0 @UiO-68-AP, [5] porphyrinbased microporous organic polymer Fe-POP-1, [6] and polyoxometalate( POM)-intercalated layered double hydroxides, [7] Pd 1 -Au 1 /LDH [8] have been reported for the synthesiso ft hese compounds through alcohol oxidation/Knoevenagel condensation tandem reactions. Although these materials were efficient for the tandemr eactions, they had some drawbacks, such as requiring ac ostly multistep synthetic route to obtain these catalysts, noble metals, and sometimes oxygen donors such as [a] Dr.
A series of Mg 2 + modified NiGa hydrotalcites have been prepared and systematically characterized, and investigated in the aerobic oxidation/ aldol condensation tandem reactions between alcohols and ketones. The results indicated that Mg 2 + in the structure could effectively enhance the surface basicity of the NiGa hydrotalcites, and significantly accelerate the aerobic oxidation/ condensation tandem reactions between aromatic alcohols and ketones. Effects of reaction conditions have been discussed, and the catalytic system exhibited good tolerance for various substrates. A series of controlled experiments proved bifunctional roles of the NiMgGa hydrotalcites in the tandem reaction.
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