1、氰基水解
腈加水可以分解為伯酰胺。由于伯酰胺會繼續(xù)水解為羧酸，一般要控制水解的條件。目前有許多方法報道，有時需要根據(jù)底物的特性選擇酸性，堿性或中性的水解條件。作為中性的條件，也有文獻(xiàn)報道使用鎳或鈀催化劑的方法。
在酸性條件下與飽和碳相連的氰基，可以在酸中很方便的水解轉(zhuǎn)化為酰胺，并在條件較為劇烈時，很容易進(jìn)一步水解成酸。但乙烯基或芳基腈的水解條件則要求劇烈得多，一般需要強(qiáng)酸條件，而且一般不會進(jìn)一步水解。
在堿性條件下，利用過氧化氫氧化的方法可在室溫下短時間內(nèi)水解腈為伯酰胺，這是一個較為可靠的方法。利用 NaOH(aq.)-CH 2 Cl 2 相轉(zhuǎn)移催化體系，DMSO-K 2 CO 3 體系可以用于各種腈水解為伯酰胺。
鹽酸水解腈為伯酰胺示例
In a 3-l. three-necked round-bottomed flask equipped with glass joints are placed 200 g. (1.71moles) of benzyl cyanide and 800 ml. of 35% hydrochloric acid. The flask is fitted with a reflux condenser, a thermometer, and an efficient mechanical stirrer. At a bath temperature of about 40° the mixture is stirred vigorously. Within a period of 20–40 minutes the benzyl cyanide goes into solution. During this time, the temperature of the reaction mixture rises about 10° above that of the bath. The homogeneous solution is kept in the bath with, or without, stirring for an additional 20–30 minutes. The warm water in the bath is replaced by tap water at about 15–20°, and the thermometer is replaced by a dropping funnel from which 800 ml. of cold distilled water is added with stirring. After the addition of about 100–150ml., crystals begin to separate. When the total amount of water has been added, the mixture is cooled externally with ice water for about 30 minutes. The cooled mixture is filtered by suction. Crude phenylacetamide remains on the filter and is washed with two 100-ml.
portions of water. The crystals are then dried at 50–80°. The yield of crude phenylacetamide is 190–200 g. (82–86%).
濃硫酸水解不飽和腈為伯酰胺示例
To 106 g of 84 % sulfuric acid, was added 50 g of acrylonitrile. After stirring for 30 min at r.t., the resulting mixture was heated to 95 ℃, and stirred for 2 h. After cooling, the solid was collected by suction, and the filter cake was transferred into a beaker. To the ice-cooled solid, was added aq. ammonia with the speed that keep the temperature less than 50℃. The precipitated ammonium sulphate was filtered off, and the filtrate was cooled. The precipitate was collected by filtration, and the filter cake was washed by water, dried in vacuum to give the desired product.
H 2 O 2 -K 2 CO 3 -DMSO 體系水解腈為伯酰胺示例
To a stirred solution of 4-chlorobenzonitrile (1.37 g, 0.01 mol) in DMSO (3 ml), cooled in a ice bath, was added 30% H 2 O 2 (1.2 ml) and K 2 CO 3 , the reaction was allowed to warm up to r.t. (strong exothermic effect was observed). After 5 min., distilled water (50 ml) was added, cooling applied, and the product was collected by filtration, yield 85%.
NaOH(aq.)-CH 2 Cl 2 相轉(zhuǎn)移催化體系水解腈為伯酰胺
To a magnetically stirred dichloromethane solution (1.5 ml) of o-tolunitrile (0.5 g, 4.27 mmol) cooled in an ice ba th, are added 30% hydrogen peroxide (2.0 ml), tetrabutylammonium hydrogen sulfate (0.290 g, 0.85 mmol), and a 20% aqueous solution of sodium hydroxide (1.6 ml). The reaction mixture is allowed to warm up to r.t. and maintained under stirring. After 1.6 h, dichloromethane is added, the organic layer is separated, washed with brine, and dried with sodium sulphate. The solvent is removed under reduced pressure to leave a white solid from which pu re o-toluamide is obtained by chromatography on silica gel. Yield 0.485 g (97%).
