【硝化反应】烯烃的硝化反应（下）

烯烃在常压常温一氧化氮（NO）作用下，可以以很好的收率制备得到相应的硝基烯烃，同时有20%的β-硝基醇生产。而硝基醇副产物在酸性氧化铝作用下脱氢后可以完全转化为相应的硝基烯烃。这个简便的硝化方法已经成功地应用于制备各类端基烯烃或苯乙烯衍生物的硝化物。这个方法后来经过修改，用H-沸石取代了氧化铝的使用。这个催化剂因为没有腐蚀性，而且能够再生和重新使用，使该反应体系得到了很大改善¹。

The R.B. flask containing a solution of olefin (132 mg, 1.0 mmol) in CCl₄(25 mL) and HY-Zeolite (2.0 g) was evacuated and filled with nitric oxide gas(1.0 atm.) Then the solution was stirred at 75 ^oC for 2 h. The reaction mixture was filtered after 2 h through a Celite pad and the zeolite was washed with CCl₄ (3×25 mL), followed by removal of CCl₄ and purification furnished 1-nitro-4-phenyl-1-butene in 81%yield.¹

在25-73 °C下，亚硝酸钠（10 eq）和Ce(NH₄)₂(NO₃)₆(2 eq)可以在超声条件下对烯烃硝化，得到很好的收率。如，环己烯通过此方法以96%的产率转换为1-硝基环己烯²。

Treatment of the alkene (0.49 mmol, 1.0 equiv.) with sodium nitrite (10equiv.), cerium(IV)ammonium nitrate (CAN, 2.0 equiv.), and acetic acid (12equiv.) in chloroform (7.0 mL) in a sealed tube. After sonication (600 W) at 25-73 ^oC for 4 h, the corresponding α,β-unsaturated nitroalkene was obtained with 99% yield upon queous workup and purification with silica gelchromatography.²

如果反应时在乙腈中进行，碳正离子中间体会被乙腈捕获而以高收率得到硝基乙酰胺³。类似的硝基乙酰胺化反应也可以在乙腈和硝基四氟硼酸酯作用下发生⁴

A solution of styrene (10 mmol) in dichloromethane was added rapidly to a solution of nitronium tetrafluoroborate (10 mmol) in a mixture of acetonitrile(20 mL) and dichloromethyane (20 mL) at -70 ^oC (bath temperature). After 5 min aqueous sodium hydrogen carbonate (10 mL) was added and the mixture was allowed to warm to room temperature. The organic solvents were then evaporated off and the residue was extracted with dichloromethane (3×20 mL). Evaporation of the dried (MgSO₄) combined extracts gave a crude product which was purified by flash chromatography on silica gel (ethyl acetateeluant) to give N-(2-Nitro-1-phenylethyl)acetamide with 84% yield.⁴

使用亚硝酸钠和碘，在乙酸乙酯，水和乙二醇存在下，烯烃可以以49-82％的收率得到共轭的硝基烯烃⁵。硝基碘的制备方法已经有所改善，是使用亚硝酸钾，碘，18-crown-6,四氢呋喃下超声得到，如下面例子中所示⁶。

A mixture of 18-crown-6 (661 mg, 2.5 mmol), KNO₂ (220 mg, 2.58 mmol) and anhyd THF (5 mL) was sonicated at r.t. under N₂ for 5 min. To the above mixture, iodine crystals(688 mg, 2.71 mmol) were added and sonication was continued for 30 min. The dark reaction mixture was then treated with a solution of 1,2-dihydronaphthalene (119 mg, 0.91 mmol) in anhydrous THF (1 mL) and pyridine(0.3-0.5 mL). After stirring for 1.5 h under N₂, Et₃N (1 mL) was added and stirring was continued for another 30-120 min. the solvent was evaporated under reduced pressure. The residue was dissolved in CH₂Cl₂ (25 mL) and washed with aq Na₂S₂O₃ solution (2×50 mL). The organic phase was dried (MgSO4), filtered (Celite), and evaporated to yield a dark residue, which was purified by flash chromatography on silica gel with 20% EtOAc/hexanegave 143 mg (90%) of pure product.⁶

使用亚硝酸钠和磺酰卤化物进行硝基磺酰化或使用苯基溴化硒，亚硝酸银和氯化汞进行的硝基硒化，对烯烃合成共轭硝化烯烃都可能是可行的方法，如下面例子所示⁷。

To a stirred solution of benzeneselenenyl bromide (7.56 g, 32mmol) in THF (40 mL) was added vinylsilane 1 (4.6 mL, d = 0.690, 32 mmol) at -78 ^oC under argon. After stirring at this temperature for 10 min, finely powdered mercury(II) chloride (13.0 g, 48 mmol) was added all at once. To the suspension was then added dropwise a solution of silver nitrite (5.12 g,33 mmol) in dry acetonitrile (40 mL) over 0.5 h at -78 ^oC. After being stirred for 8 h, the reaction mixture was allowed to warm to room temperature. The resulting white precipitates of silver chloride were removed by filtration, and the filtrate was concentrated in vacuo. The residue was then subjected to silica gel column chromatography to provide the corresponding nitroselenide (6.34g, 66% yield). To a vigorously stirred solution of the nitroselenide (2.40 g, 8mmol) in dichloromethane was injected 30% aqueous hydrogen peroxide (1.8 mL, 16mmol) at 0 ^oC and the mixture was stirred for 30 min. The usual ethereal workup provided an oil, which was passed through a silica gel column to give 2 (1.03g, 89% yield).⁷

共轭二烯烃在三氟乙酸条件下与硝酸铵反应可以以很高的收率得到对应的 1-硝基-1，3-二烯烃⁸。

Ammonium nitrate (8 g, 0.1 mole) was added portionwise to a solution of 1,3-butadiene (7g, 0.12 mole) in dichloromethane (100 ml) containing trifluoroacetic anhydride (20 mL) and fluoroboric acid (0.5 ml, 40% aq. solution) at 35 ^oC. The rate of addition was such that gentle reflux was maintained. After the addition was complete the solution was allowed to cool to room temperature and water (100 mL) was added. The organic phase was washed with brine (5 x 100 ml) and dried over magnesium sulphate. Removal of the solvent under reduced pressure afforded a crude residue purified by filtration chromatography (silica gel-dichloromethane). To a portion of the purified mixture of nitrotrifluoroacetates (2 g) in ether (20 mL) anhydrous potassium acetate (1.9 g, 2 mmole) was added and the mixture was stirred at room temperature for 18 h. (TLC. analysis showed complete loss of nitrotrifluoroacetates). The ethereal solution was washed with brine, dried over magnesium sulphate, and the solvent removed to afford crude product, which was purified by distillation to give 1-nitro-1,3-butadiene (0.84 g) (89% yieldfrom 1,3-butadiene).⁸

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