硝基的還原是一種常用的合成伯胺的方法特別是芳香伯胺，一般而言，最干凈和簡便的還原方法就是通過Pd/C或Raney Ni加氫，但是當分子內(nèi)存在對加氫敏感的官能團，如：鹵素（Cl, Br and I; F 對加氫不敏感），雙鍵，三鍵時，我們不得不采用其他方法， 最為經(jīng)典的要數(shù)鐵粉的還原。
反應實例
To the starting material (3.1 g) was added acetic acid (24.4 mL) and then, reduced iron powder (9.15 g), and the mixture was stirred for 16 hours at room temperature. The mixture was filtered with Celite, and washed with ethyl acetate. The solvent was removed under reduced pressure, and water was added to the obtained residue, and the mixture was extracted with ethyl acetate. The organic layer was washed with saturated brine, and dried over magnesium sulfate. The solvent was removed under reduced pressure, and the obtained residue was purified by silica gel column chromatography, to give 1.4 g of the desired
product.
To 80 percent ethanol (5.0 mL), the starting material (300 mg, 1.76 mmol) and concentrated hydrochloric acid (0.45 ml, 5.28 mmol) were added to stir for 10 minutes at 20°C. Then, iron powder (500 mg, 8.95 mmol) was added to the mixture to further stirring for 1 hour at 20°C. Insoluble matters were filtered off and the filtrate was concentrated, adding 0.5N NaOH (10 mL) to the residue, filtering the solution to further remove insoluble matters, extracting the filtrate with chloroform, drying the extract over anhydrous sodium sulfate, concentrating the extract, and distilling the resulting crude product to afford 224 mg of the
desired compound (91% yield).
另外常用的條件還有，鐵粉，氯化銨在甲醇和水混合溶液中回流。此類反應的后處理，一般情況下都是趁熱過濾，防止冷卻后，產(chǎn)品吸附到剩余的鐵粉和氧化鐵上。
另外由于鐵粉反應后氧化物的顏色較深，不好純化，有時會用鋅粉代替鐵粉進行反應，條件類似。
