烯烃的氢化

产物官能团类型

1. H2-Pd/C 2. H2-PtO2 3. HCO2NH4-Pd/C 4. Zn 5. NaBH(OAc)3 6. LiAlH4

1. H2-Pd/C

使用碳载钯催化剂 (Pd/C) 的催化加氢是一种非常常见的烯烃还原方法。典型的溶剂包括甲醇 (MeOH)、乙醇 (EtOH) 和乙酸乙酯 (EtOAc)。

案例

A mixture of the SM (7.2 g, 26.2 mmol) and 10% Pd/C (2 g) in MeOH (100 mL) was stirred under an atmosphere of H2 (50 psi) at RT for 12 h. The mixture was filtered through celite and the filtrate was concentrated. The residue was purified by silica gel flash chromatography to provide the product. [5.8 g, 80%]

Patent Reference: WO2016014463, page 102

2. H2-PtO2

使用氧化铂(IV) (PtO2) 的催化加氢能够有效地还原烯烃。对于那些芳香卤化物脱卤存在顾虑的底物，PtO2 通常被用来代替碳载钯催化剂 (Pd/C)。

案例

A solution of the SM (2.435 g, 5.99 mmol) in EtOH (20 mL) was treated with PtO2 (0.136 g, 0.599 mmol), and was placed under 45 psi H2 for 1 h. LCMS indicated mostly product and de-brominated product. The mixture was diluted with DCM and filtered through celite. The filtrate was concentrated then purified directly by column chromatography (0-15% EtOAc/heptane) to provide the product. [0.970 g, 39.6%]

Patent Reference: WO2014201173, page 63

3. HCO2NH4-Pd/C

使用甲酸铵和碳载钯催化剂 (Pd/C) 进行催化转移氢化是还原烯烃的一种常见方法。与氢气相比，甲酸铵更易于操作，并且精确测量当量更加简单。

案例

A solution of the SM (2.5 g, 7.1 mmol), ammonium formate (2.6 g, 43 mmol), 10% Pd/C (379 mg, 0.3 mmol) in THF (10 mL) and MeOH (30 mL) was refluxed for 90 min. The mixture was filtered through celite and the celite pad was washed with EtOAc. The filtrate was concentrated to provide 3.8 g of material. The material was partitioned between EtOAc/H2O. The org layer was separated, dried (MgSO4), and concentrated to provide the product which was taken to the next step without further purification. [2.2 g, 87%]

Patent Reference: WO2015144799, page 181

4. Zn

锌通常无法还原孤立的双键。但当双键与电子吸引基团 (EWG) 共轭时，锌的还原能力得以实现。这一过程在电子吸引基团（如苄基酮）在氢化条件下容易被还原的情况下非常有用。

案例

A mixture of the SM (1.38 g, 5 mmol), Zn dust (1.95 g, 30 mmol), NH4Cl (2.67 g, 50 mmol), MeOH (10 mL), and H2O (5 mL) were refluxed for 4 h. The mixture was cooled to RT, filtered, and the filtrate concentrated. The resulting residue was purified by chromatography (5:1 PE/EtOAc) to provide the product as a brown solid. [1.15 g, 83%]

Patent Reference: WO2016023832, page 71

5. NaHB(OAc)3

三乙酰基硼氢化钠 (NaHB(OAc)3) 是一种用于还原烯胺的有效试剂。尽管其他试剂也可以实现相同的还原反应，但当需要温和条件并具有较高的官能团耐受性时，NaHB(OAc)3 是一个不错的选择。

案例

To a solution of the SM (crude) in DCE (50 mL) at 0 C was added NaBH(OAc)3 (3.6 g, 17.1 mmol). The reaction mixture was stirred at 0 C for 2 h, after which time excess reagents were consumed by the addition of sat aq Na2CO3. The mixture was extracted with EtOAc and the org phase was washed with brine and concentrated in vacuo. The residue was purified by silica gel flash chromatography to provide the product. [1.4 g, 62% over 2 steps]

Patent Reference: WO2016014463, page 64

6. LiAlH4

铝氢化锂 (LiAlH4) 通常不还原烯烃，但与硝基共轭的烯烃（硝基烯烃）通常可以用 LiAlH4 还原。在还原过程中，硝基也会被还原。这种方法在使用 Henry 反应生成硝基烯烃后是一个常见的步骤。

案例(此处案例参考四氢铝锂将硝基还原成氨基的反应)