对硝基苯甲酸
上保护
一、对硝基苯甲酰氯，咪唑，产率大于52%。
【Tetrahedron, 56, 4367 (2000)】
其他文献
【Chem. Commun., 2788 (2003)】
【J. Carbohydr. Chem., 9, 873 (1990)】
二、 Mitsunobu法保护羟基：对硝基苯甲酸，三苯基膦，DEAD，THF。此方法对于手性醇构型会发生反转。
A 250-mL, three-necked, round-bottomed flask isequipped with a stirring bar, nitrogen inlet, rubber septum,and thermometer. The flask is charged with 3.00 g of (1R, 2S, 5R)-(?)-menthol (19.2 mmol), 12.9 g of 4-nitrobenzoic acid (77.2 mmol),20.1 g of triphenylphosphine (PPh3) (76.6 mmol), and 150 mL of tetrahydrofuran.The flask is immersed in an ice bath, and 12.1 mL of diethyl azodicarboxylate (77 mmol) is added dropwise at a rate such that thetemperature of the reaction mixture is maintained below 10°C. Upon completionof the addition, the flask is removed from the ice bath and the solution isallowed to stir at room temperature overnight (14 hr) and subsequently at 40°Cfor 3 hr. The reaction mixture is cooled to room temperature, diluted with 150 mL of ether, and washedtwice with 100 mL portions of saturated aqueous sodium bicarbonate solution. The aqueous layers arecombined and back-extracted with 100 mL of ether. The combined organic layers are dried over sodium sulfate. Excess solvent and other volatilereaction components are completely removed under reduced pressure initially ona rotary evaporator and then under high vacuum(approximately 0.2 mm for 3 hr at 30°C). The resulting semi-solid is suspendedin 40 mL of ether andthe suspension is allowed to stand at room temperature overnight. The mixtureis stirred while 20 mL of hexanes is slowly added.The resulting white solid is filtered under vacuum and the filter cake iswashed with 200 mL of 50% (v/v) ether-hexanes.The solvent is removed from the filtrate on a rotary evaporator under reducedpressure to give a yellow oil that is dissolved in 10 mLof methylene chloride and diluted with 40 mL of 8% ether-hexanes. The solution isapplied to a flash chromatography column and eluted with 8%ether-hexanes to give 5.03 g (85.6%) of pure nitrobenzoate ester as a white crystallinesolid.
【 Organic Syntheses,Coll. Vol. 9, p.607; Vol. 73, p.110.】
【 Tetrahedron. Lett. 1995, 36,7189.】
【J. Org. Chem., 2005, 70 (19), pp 7592–7604】
去保护
一、NaOH，dioxane/水，产率大于97%。【Tetrahedron, 56, 4367 (2000)】
二、碳酸钾，甲醇，产率大于92%。
【 Tetrahedron. Lett. 1995, 36,7189.】
三、叠氮化钠，甲醇，40℃，52-100%产率，此方法条件温和，Aldol酯在反应中不会消除。
编译自： Protective groups in organic synthesis (Wuts & Greene,4th Ed), P: 264.
