《Table 3Reusability tests of Pd NPore in the reduction of quinoline a.》

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《非负载纳米多孔钯催化喹啉及其衍生物的化学选择性氢化反应:H_2分子异裂（英文）》

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a Reaction conditions:quinoline（1a，0.5 mmol），Pd NPore（5 mol%），H2（5 atm），in CH3CN（3.0 m L）at room temperature for 24 h.b Isolated yield.

The hydrogenation of quinoline（1a，Table 1）in the pres‐ence of Pd NPore（5 mol%）was chosen as a model in prelimi‐nary tests aimed to optimize the reaction conditions.The re‐sults are shown in Table 1.It was expected that a polar and Lewis‐basic solvent could assist the heterolytic cleavage of H–H bonds，facilitating the chemoselective hydrogenation of quino‐line to py‐THQ[24，42].Accordingly，the reduction was initially tested in polar and Lewis‐basic solvents，dimethylformamide（DMF），and 1，4‐dioxane（Dioxane），under 5 atm H2 at room temperature.As expected，2a was obtained as the sole product in moderate yields（entries 1 and 2，55%and 51%，respective‐ly）.The yield of 2a decreased when toluene，a nonpolar solvent，was used（entry 3，30%）.In contrast，the yield of 2a increased to 72%by adding triethylamine（Et3N），a polar and Lewis‐basic additive，to toluene（entry 4）.Thus，Et3N was used as the sol‐vent，and the yield of 2a further increased（entry 5，80%）.The desired product 2a was finally obtained in excellent yield（93%）when acetonitrile（CH3CN）was used as a solvent（entry6）；in this case，ethylamine（1.5 mmol）was also obtained.These results indicate that CH3CN was hydrogenated to the corresponding amine under the reaction conditions.The ob‐tained ethylamine may act as a polar and Lewis‐basic additive，in addition to CH3CN itself.The yield decreased when the H2pressure and catalyst loading were decreased（entries 7 and 8）.The yield of the 2a product also decreased with a shorter reac‐tion time（entry 9）.No reaction was observed in the absence of Pd NPore catalyst or when the precursor of Pd NPore，the Pd20Al80 alloy，was used in the hydrogenation of 1a（entries 10and 11）.Accordingly，we set the standard conditions as follows:Pd NPore（5 mol%），5 atm H2，and room temperature in CH3CN.The desired 2a product was separated in low yield，along with a N‐ethyl‐1，2，3，4‐tetrahydroquinoline byproduct，when the palladium/carbon and the Lindlar palladium catalysts were used instead of the Pd NPore catalyst（entries 12 and 13）.These results clearly indicate that the activity and selectivity of the Pd NPore catalyst are higher than those of the two commercial‐ly available catalysts.