Supporting Information: Hydrotalcite-Supported Ag/Pd Bimetallic Nanoclusters Catalyzed Oxidation and One-pot Aldol Reaction in Water

A highly active hydrotalcite-supported Ag/Pd bimetallic nanocluster catalyst has been developed by a simple, easy and safe chemical reduction method. The catalyst was characterized by high-resolution transmission electron microscopy (HR-TEM), which revealed very small (3.2 ± 0.7 nm) nanoclusters with a narrow size distribution. The bimetallic Ag/Pd catalyst showed strong cooperation between Ag and Pd for the alcohol oxidation reaction. The developed catalyst provided an efficient and environmentally friendly method for alcohol oxidation and one-pot cross-aldol condensation in water. A broad scope of α,β-unsaturated ketones with good to excellent yields were obtained under very mild conditions. This catalytic system offers an easy preparation method with a simple recovery process, good activity and reusability of up to five cycles without significant loss in the catalytic activity.


Preparation of Hydrotalcite (HT)
Mg/Al hydrotalcite (HT) was prepared as described in previous methods. Briefly, a 100 ml solution containing 30 mmol of Mg(NO3)2.6H2O and 10 mmol of Al(NO3)3.9H2O (Mg/Al=3/1) was slowly dropped over 100 ml of 0.3M Na2CO3. The solution was kept under vigorous stirring for 1h. During precipitation, the pH of the solution was kept constant at 10 at 60 ⁰C by using 1M aq. NaOH. The suspension was continued to stir at 60 ⁰C for more 1 h and the solid was obtained after centrifugation. It was washed with water 3 times and dried at 100 ⁰C for 24h.

Preparation of Silver; Palladium or Silver/Palladium bimetallic nanoclusters:
0.025 mmol 12.5 mM aq. Pd(OAc)2 or AgOAc solution was mixed with 300 mg of HT. Then, 2.5 mmol, 0.27 mM aq. NaBH4 was added and stirred at room temperature for 1 h. The catalyst after washing several times by deionized water and drying under vacuum was directly used for reaction. 0.0125 mmol 12.5 mM aq. Pd(OAc)2 solution and 0.0125 mmol AgOAc was mixed with 300 mg of HT. Then, 2.5 mmol, 0.27 mM aq. NaBH4 was added and stirred at 15 ⁰C for 1 h. The catalyst after washing several times by deionized water and drying under vacuum was directly used for reaction.

Procedure for time profile and hot filtration test
For the time profile, several parallel reactions for one-pot oxidation and aldol reaction were carried out taking 1-indanol (0.1 mmol), 4-methoxybenzaldehyde (0.3 mmol), Cs2CO3 (150 mol%) and Ag/Pd catalysts 5 atom% in 13-mm test tubes. The oxygen gas was supplied from the balloon. 1 ml solvent (dioxane/H2O, 1:3) was added and stirred at 1200 rpm at 70 °C for the desired time. The reactions were stopped at different intervals, centrifuged and washed at least 3 times with acetone. The acetone layer were collected, evaporated and filtered through a celite. The NMR spectra were recorded to check the ratio of product and the starting material at different time intervals.
For hot filtration test, two parallel sets of reactions were conducted under the optimized reaction condition in test tubes (13 mm) using an organic synthesizer as follows. 1-indanol (0.1 mmol), 4-methoxybenzaldehyde (0.3 mmol), Cs2CO3 (150 mol%) and Ag/Pd catalysts 5 atom% were placed in test tubes. The oxygen gas was supplied from the balloon. 1 ml solvent (dioxane/H2O, 1:3) was added and stirred at 1200 rpm at 70 °C for 3h. Both reactions were stopped at 3h and the catalyst was removed by centrifugation and filtration. One of the reaction mixture, after evaporation, immediately analyzed by NMR (entry 1), while another reaction mixture was continued for another 4 h without catalyst (entry 2). Then it was evaporated and analyzed by NMR.

Reusability test
The oxidation reaction of 1-indanol and one pot aldol reaction with 4-methoxybenzaldehyde was performed following the general reaction procedure in a test tube (30 mm) using an organic synthesizer. After completion of the reaction, the reaction mixture was transferred to a centrifuged tube and acetone was added. It was centrifuged and washed three times with acetone (45 ml each) and finally with water. The acetone was collected, evaporated and purified to get isolated yield of the product in each cycle. The catalyst was dried after the first catalytic cycle and used for the next run.   149.8, 138.1, 135.5, 134.9, 134.8, 134.8 134.1, 130.8, 130.8 129.8, 129.1, 127.8 2-(4-Chlorobenzylidene)-indan-1-one1