硝酸/酸酐硝化反应

一、硝酸/乙酸酐

硝酸和乙酸酐混和，生成乙酸酸和硝酸的混酐（CH3COONO2），是一个良好的硝化试剂，反应条件比较温和。

反应实例：

A 1 L three-necked round-bottomed flask, fitted with a dropping funnel and a

mechanical stirrer, is cooled in an ice-salt mixture. To the flask are added freshly distilled cinnamaldehyde (55.5 g, 50 mL, 0.42 mole) and of acetic anhydride (225 mL). When the temperature of the solution has reached 0–5°C, a solution of concentrated nitric acid (sp. gr.1.42, 18 mL) in glacial acetic acid (50 mL) is added slowly through the dropping funnel while the mixture is stirred. The time of addition is 3–4 hours, during which the temperature is kept below 5°. After the addition is complete, the mixture is allowed to warm slowly to room temperature. The reaction flask is then dismantled and stoppered, and the reaction mixture is allowed to stand 2 days.

At the end of this time, hydrochloric acid (20%) is added cautiously to the cooled

solution until a precipitate begins to appear. The addition of acid is then stopped, and the solution is allowed to cool in an ice bath or refrigerator until precipitation of the solid is completed. The light-yellow needles are collected on a Büchner funnel and dried in air. About 24 g of o-nitrocinnamaldehyde, mp 125–127°, is obtained. Additional product can be isolated by cautiously adding water to the mother liquor until precipitation is observed and then cooling the resultant mixture for several hours in an ice bath. Recrystallization from 95% ethanol gives 5–10 g. of o-nitrocinnamaldehyde, mp 126–127°. The total yield is 27–34 g (36–46%).

【Organic Syntheses, Coll. Vol. 4, p.722; Vol. 33, p.60】

二、硝酸/三氟乙酸酐

硝酸和三氟乙酸酐也是一个类似的硝化试剂，硝酸也可用硝酸铵代替。

反应实例：

A mixture of trifluoroacetic anhydride (10 mL) and fuming nitric acid (2.4 mL) was

chilled at –15ºC and after 1 h a solution of furan-2-carbaldehyde (0.96 g, 10 mmol) in trifluoroacetic anhydride (2 mL) was slowly added to the reaction mixture keeping the temperature at -15ºC. The reaction mixture was stirred at -15ºC for 2 h and then the solvents were removed and pyridine (2 mL) was added to the reaction mixture, stirred for 15 min. And then the solvent was again removed and the oily residue was poured in ice and extracted with diethyl ether. The crude product was then purified over a silica gel column to give the pure

product (0.96 g, 68 %).

【 Katritzky, A.R; Scriven, E. F. V; Majumder, S. ARKIVOC, 2005, 179】

5-Methylisoxazole (8.31 g, 0.1 mol) was dissolved in trifluoroacatic anhydride (74 g, 0.35mol= 50 mL, d = -1.487 g/mL), and ammonium nitrate (8.00 g, 0.100mol) was added in 0.5-g portions, keeping the reaction temperature between 25 and 30 'C. After complete addition, 'H NMR of a neat aliquot showed the mixture to contain 65% product and 35% starting isoxazole. Thus, another portion of ammonium nitrate (3.60 g, 0.045 mol) was added as above. After complete addition, 'H NMR analysis indicated that less than 5% of starting material

remained. The mixture was poured onto ice water and extracted with chloroform (4 X 50 mL). The extracts were washed with water (250 mL), and this aqueous wash was extracted with chloroform (3 X 25 mL). The combined chloroform extracts were dried over magnesium sulfate and filtered, and the filtrate was concentrated giving a yellow oil [12.34 g (96%)], which was virtually pure as determined by 'H NMR. The oil was distilled to give the product (8.04 g, 63%) as a pale yellow liquid: bp 88-90 'C (18 Torr).

【 L.A.Reiter, J.org.Chem. 1987, 52, 2714】