利用Pd/C或Raney Ni催化加氫還原硝基是合成胺的最干凈和簡便的還原方法。
反應實例
一、芳香硝基Pd/C 加氫還原
To a solution of the starting material (10 g) in 200 ml of ethanol was added 1.03 g of 10 percent Pd/C and the mixture was stirred for two hours at room temperature in a hydrogen atmosphere under atmospheric pressure. Insoluble matters were removed using Celite, and the filtrate was concentrated in vacuo to give 9.54 g of the product.
二、脂肪硝基Pd/C 加氫還原
To a solution of the starting material (3 g, 16 mmol) in ethanol (100 mL) was added 10 percent Pd/C (1 g) and the resulting mixture shaken under a hydrogen atmosphere (4 bar) for 3 days. The catalyst was removed by filtration and the solvent evaporated. To the resulting oil was added a saturated solution of ethanolic hydrochloric acid (5 mL) and the solvent was evaporated. Addition of ether gave a white solid which was collected and washed with ether to provide 3-amino-1,1,1-trifluoro-2-pentanol hydrochloride (1.3 g) as a white solid; TLC: Rf
=0.1, methanol:dichloromethane (10:90).
三、芳香硝基 Raney Ni 加氫還原
To a suspension of the above product (6.1 g, 29.6 mmol) in ethanol (170 mL) was added Raney nickel (0.5 g) and the resultant mixture was hydrogenated at ambient pressure until the hydrogen uptake had ceased. Filtration through celite and evaporation of the solvent from the filtrate left the desired product, quantitatively.
四、脂肪硝基 Raney Ni 加氫還原
To the starting material (1.00 g, 5.88 mmol) and NaOH (0.235 g (5.88 mmol) in 5 mL of ethanol, 0.40 g of Raney nickel were added to stir the mixture under hydrogen atmosphere at 20.deg. C. for 12 hours. The catalyst was filtered off, and then the filtrate was poured into 33percent HCl/isopropanol (5.0 mL) below 20.deg. C. The reaction mixture was evaporated to dryness to give crude crystal. The crude crystal was suspended in toluene (5.0 mL) and to the suspension was introduced NH3 gas to stir at 20.deg. C. for 12 hours. The precipitate was filtered off and the filtrate was evaporated to afford 716 mg of the desired compound (Yield:86.9%).
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