Rosenmund还原反应是催化氢化还原反应，指酰氯在部分失活的钯催化剂（Pd/BaSO4）作用下用氢气进行还原，得到相应的醛。反应由德国化学家 Karl Wilhelm Rosenmund (1884-1965) 首先报道。

酰氯在 BaSO4，喹啉-S或硫脲钝化的Pd催化剂的催化下氢化还原得到醛的反应。如果不进行钝化，生成的醛会继续还原成醇，因此可能的副产物有醇，酯和烷烃等。反应常用的溶剂有甲苯、二甲苯、THF等等，通常要求严格无水条件下进行，否则会有酸酐类副产物生成。

反应机理

反应是通氢气于悬浮有催化剂的酰氯溶液中来进行。是从羧酸合成醛的方法之一，一般应用于制备一元脂肪醛和一元芳香醛。反应的副产物有醇、烷烃、酸酐和酯。用三叔丁氧基氢化铝锂也可以将酰氯还原为醛。此外，芳香酰氯也可在钯络合物催化下用聚甲基氢硅氧烷（PMHS）还原为芳醛。亦可用三丁基氢化锡来进行或在氢供体存在下用光照射来还原。

一般需要使催化剂中毒以防止进一步的还原作用，最常用的中毒剂是硫-喹啉（由硫在喹啉中回流来制备）和硫脲。除了硫酸钡，其他活性调节剂，如2,6-二甲基吡啶（Pd/C）也可使用。

反应案例

A pressure vessel is charged in order with 600 mL of dry toluene,25 g. (0.30 mole) of anhydrous sodium acetate,3 g. of dry, 10% palladium-on-carboncatalyst,23 g. (0.10 mole) of 3,4,5-trimethoxybenzoyl chloride, and 1 mL of Quinoline S. The pressure vessel is flushed with nitrogen, sealed, evacuated briefly, and pressured to 50 p.s.i. with hydrogen. The mixture is shaken with 50 p.s.i. of hydrogen for 1 hour at room temperature, then heated at 35–40° for 2 hours. Agitation is continued overnight while the reaction mixture cools to room temperature. The pressure on the vessel is released, the vessel is opened, and the mixture is filtered through10 gof Celite filter aid, and the insoluble material is washed with 25 mL of toluene. The combined filtrates are washed successively with 25 mL of 5% sodium carbonate solution and 25 mL of water. The toluene solution is dried over5 gof anhydrous sodium sulfateand filtered. The filtrate is concentrated by distillation at reduced pressure using a water aspirator. The residue is distilledthrough a 10-cm. Vigreux column with warm watercirculating through the condenser, to preventcrystallization of the distillate, yielding 12.5–16.2 g (64–83%) of 3,4,5-trimethoxybenzaldehyde, b.p. 158–161°C(7–8 mmHg.), m.p. 74–75°C.

反应经验

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