还原性金属氯化物还原硝基制备胺

还原性的金属氯化物（如二氯化锡，三氯化钛等）可以将硝基还原为胺基，此类方法一般不还原双键，也不会脱卤。

反应实例

1、二氯化锡还原硝基化合物实例

A stirred solution of stannous chloride dihydrate (38 g, 0.183 mol) in concentrated hydrochloric acid (100 ml, 1.2 mol) was treated portionwise with the starting material (10 g). Ethanol (10 mL) was added to clarify the solution and the mixture is stirred at 60 °C for 3 hours. The solution was evaporated to near dryness and three 100 mL. portions of ethanol are added sequentially and evaporated from the residue. The residual syrup was stirred with 800 mL. of ether and the resulting solid is collected by filtration, washed with ether and dried

at reduced pressure. This solid (a tin complex) is dissolved in 150 mL of water and the tin is precipitated as the sulfide by bubbling hydrogen sulfide gas into the solution. The mixture is filtered and the filter cake washed with water. The filtrate and washings are combined and evaporated at reduced pressure. The residue is repeatedly evaporated with 100 mL portions of ethanol. The final residual gum is triturated with 30 mL of ethanol to give as a crystalline solid product dihydrochloride, which is collected by filtration, washed with ethanol and dried

at reduced pressure; m.p. 155 °C.

2、二氯化锡还原脂肪硝基化合物

A mixture of 106.6 g (0.41 mol) of the above material, 350 g (1.5 mol) of SnCl2.H2O, 1 L of MeOH, and 350 ml of AcOH was stirred and refluxed for 3 hr. The reaction mixture was then partly concentrated (500 ml collected), cooled, and treated portionwise with a cold solution 700 g of K2CO3 in 1 L of H2O. Ether (600 mL) and CHCl3 (200 mL) were added and the mixture was shaken. The layers were separated and the aqueous phase was extracted twice with the same Et2O-CHCl3 mixture. The organic phase were combined and dried over 

MgSO4 and the solvents were removed under reduced pressure to give 90 g of residue.

Ref: J. Med. Chem., 1968, Vol.11, No.2, 361-364.

3、三氯化钛还原脂肪硝基化合物

The material (2.9 g, 7.4 mmols) was dissolved in acetone (60 mL) and the solution stirred at 5°C in an ice bath. 30 percent titanium trichloride solution (40 mL) in hydrochloric acid was added dropwise over 30 minutes and the reaction mixture stirred at 5°C for a further 45 minutes before warming to room temperature overnight. The reaction mixture was poured into water and extracted with diethyl ether. The combined ethereal extracts were washed with water, dried (MgSO4), filtered and the filtrate evaporated under reduced pressure to give

a pale yellow solid (1.7 g). This was triturated with a 1:1 petroleum/ether mixture and filtered to yield the desired product (1.2 g) as a cream solid.

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另外还有一种用水合肼和Raney Ni还原硝基的方法，也比较常用，但由于水合肼有一定的毒性而受到限制。

To a refluxing mixture of 19.2 g (0.058 mol) of the above material and 2 teaspoonsful of raney nickel in 200 mL ethanol is added over a 15-minute period a solution of 9.6 g of 99% hydrazine hydrate in 30 mL ethanol. The reaction is refluxed 1 hour, cooled, and evaporated to a residue which is dissolved in ether. The ether solution is treated with decolorizing carbon and evaporated to give 3-amino-4-benzyloxyphenyl 2-pyridyl ketone as an oil, 14.2 g (yield 86%).