将羰基转化成硝基 (retro Nef Reaction) 是制备硝基化合物的一个重要的定制合成方法。这种转化通常是通过用强氧化剂（如CF3CO3H）把肟氧化成硝基来实现1。
无水CF3CO3H很难处理，因此有文献报道了该反应的优化方法2。即用三氟乙酸酐与过氧化脲的络合物(UHP) 在乙腈中0 °C反应得到过氧三氟乙酸的溶液，将醛肟氧化得到相应的硝基化合物，并且收率较高。该方法对酮肟不适用，只能得到相应的酮。
To a stirred suspension of UHP (60 mmol, 5.8 g) in CH3CN (30 mL), TFAA (50 mmol, 10.5 g) dissolved in CH3CN (50 mL) at 0 oC. After stirring at this temperature for 4 h, most of the solvent was removed under reduced pressure and the residue was dissolved in NaHCO3 sol satd. and extracted with ether. The ethereal solution was washed with 5% Na2SO3(starch-iodide test negative) and dried over MgSO4. The crude material, after evaporation of the solvent, was purified by flash chromatography to give nitro compound with 75% yield.2
文献中还报道了很多新的方法将肟氧化成硝基化合物。Olah报道了用过氧硼酸钠在乙酸溶液把肟氧化成硝基化合物的方法3。
Bicyclo[2.2.1]norbornanone-2-oxime (1.0 g, 8 mmol) was dissolved in 50 mL of glacial acetic acid in dry three-necked round bottomed flask. The flask was immersed in an oil bath at a temperature of 55 oC. In portions, solid sodium perborate tetrahydrate (6.20 g, 40 mmol) was added with vigorous stirring over a period of 30 minutes. After the addition, the reaction mixture was stirred at the same temperature for 4 h. After cooling, the reaction mixture was treated with 4×25 mL ice cold saturated solution of sodium bicarbonate, followed by extraction with ether (2×50 mL). The organic layer was washed several times with cold water, dried over anhydrous MgSO4 and evaporated. The crude product was passed through a silica gel column eluted with chloroform-pentane (1:4). The obtained product was further purified by vacuum distillation to give 2-nitrobicyclo[2.2.1]-norbornane (0.74 g) as a yellow liquid in 65% yield.3
用Mo (IV)的过氧化合物可以将肟氧化成硝基化合物，这个方法的好处是既可以氧化醛肟也可以氧化酮肟,4可以很好的弥补UHP方法的不足。
In a typical experiment 5 mL of CH3CN containing 0.5 mmol of oxodiperoxo complex was added to a stirred CH3CN solution containing 1 mmol of the oxime at 40 oC. The progress of the reaction was monitored by following the disappearance of the peroxide(iodometric titre). The oxidation products were isolated by column chromatography (silica-gel, pentane-chloroform 4:1).
m-CPBA作为一个常用的氧化剂，也被用于某些肟转化成硝基化合物的反应5。
To a solution of m-chloroperbenzoic acid (80%, 6.45 g,0.03 mol) in a minimum volume of dichloromethane (~90 mL) is added diisopropyl 1-hydroxyimino-alkane phosphonate (0.03 mol) at room temperature. The reaction mixture is stirred and the progress of reaction is monitored by TLC (silicagel, chloroform-ethyl acetate, iodine). After about 72 h the oximinophosphonates have disappeared. The mixture is extracted with saturated aqueous sodium hydrogen carbonate containing sodium sulphite (2×50 mL), water(2×50 mL), brine (50 mL), and dried with sodium sulphate. The solvent is removed and the residue is distilled under reduced pressure to give pure diisopropyl 1-nitroalkane phosphonate with 65% yield.5
【参考文献】
1. Emmons, W. D., and A. S. Psgano. J. Am. Chem. Soc., 77, 4557 (1955).
2. Ballini, R., E. Marcantoni, and M. Petrini. Tetrahedron Lett., 33, 4835 (1992).
3. Olah, G. A., P. Ramaiah, C. S. Lee, and G. K.S. Prakash. Synlett., 337 (1992).
4. Ballistreri, F. P., E. Barbuzzi, G. A.Tomaselli, and R. M. Toscano. Synlett,1093 (1996).
5. Zon, J. Synthesis,661 (1984).
