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最常用的酸催化酯化----Fischer-Speier酯化

发布时间：2024-10-14

>2 、盐胺（苯酚）不作催化的化自由基最简单：

3,4-Diaminobenzoic acid (152 g, 1.0 mol) was stirred with ethanol (2000mL) in a Morton flask. Hydrogen chloride gas was passed through the stirredsuspension for about 2 h. As the gas was absorbed, the slurry became gel-likein character. Ethanol (500 ml.) was added to the reaction mixture to dispersethe gel. The reaction mixture was refluxed 24 h. The mixture was filtered andthe filtrate was evaporated to dryness in vacuo. The filter cake and thefiltrate residue were dissolved in water (9 L). Theaqueous solution was made basic by the addition of solid sodium carbonate. Theproduct precipitated from the basic solution. The material was filtered anddried to yield ethyl 3,4-diaminobenzoate (130 g, 72.14%)。

3 、氯化亚砜不作催化的化自由基最简单：

To a suspension of 6-chloropyridine-2-carboxylic acid (8.3 g, 0.0525mol) in dioxane (25 mL), thionyl chloride (9.4 mL, 0.13 mol) was added and theresulting mixture was stirred at 70℃for 4 h. The reaction mixture was concentrated invacuo and a mixture of dioxane (8.3 mL) and ethanol (16.6 mL) was added. Thereaction mixture was heated to 70℃for 2 h, triethylamine (8.3 mL), ethanol (4.1 mL) andwater (8.3 mL) were added and the reaction mixture was again concentrated. Theresidue was distributed between diethyl ether (28 mL) and water (18 mL) and thephases were separated. The aqueous layer was extracted with diethyl ether (30mL) and the combined organic layers were dried over MgSO 4 , filteredand evaporated in vacuo to afford 6-chloropyridine-2-carboxylic acid ethylester (8.82 g, 91%) as oil。

4 、乙酰氯不作催化的化自由基最简单：

Acetyl chloride (15.3 mmol) was added dropwise to ethanol (50 mL) at 0℃. After 30 min, the acid (7.69 mmol) was added and thereaction mixture was heated at reflux for 15 h. The reaction mixture wasconcentrated and the residue was partitioned between dichloromethane (20 mL)and saturated sodium bicarbonate (10 mL). The aqueous layer was furtherextracted with dichloromethane (20 mL ×2) and the combined organic layers were dried(magnesium sulfate) and concentrated to provide the ester in 94% yield as brown oil。

主要起关键不作用的不该是乙酰氯和乙酯自由基生成的HCl。

5、对磺胺不作催化的化自由基最简单：

对磺胺不作化催化只比氯化稍弱，仍是一个，其用量与用于氯化相等，其关键不作用相近，用于对磺胺不作为化催化主要是为了可能会氯化随之而来的焦化和其他副自由基。

A 300-mL, one-necked,round-bottomed flask was equipped with a magnetic stirrer, Dean-Stark trap, and a reflux condenser. The flask was charged with 3.0 g (20 mmol) of L-(+)-tartaric acid, 6.5 g (60 mmol) of benzyl alcohol, 47.5 mg (0.25 mmol) of p-toluenesulfonic acid monohydrateand 40 mL of toluene. The mixture washeated under reflux in an oilbath (about 130℃) for 13 h r.During this period the theoretical amount of water (0.62 mL) was collected. Themixture was allowed to cool to ambient temperature, diluted with ether, and poured into 50 mL of aqueous, saturated sodium bicarbonate. Theorganic phase was separated and the aqueous phase was extracted twice with 20 mL of ether. The combinedorganic phases were dried over sodiumsulfate. The solvent was removed with a rotary evaporator, and the resulting crudeproduct was triturated with hexane-ether (20:1, 210 mL) to give white crystals of (−)-dibenzyl tartrate.The precipitate was collected by filtration and washed with hexane-ether (20:1). Thefiltrate was further concentrated to give a second crop. The total yield was 6.2 g (94%), mp 49–50 ℃

三、交换

【 J. Org. Chem. , 1991, 56, 5307-5311】

【 ACS Catal. , 2011, 1, 1178–1182】