Trichloromethylation reaction. Ring-chain tautomerism
Trichloromethylation reaction. Ring-chain tautomerism
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三氯甲基化反应。
DOI：
10.1021/jo01282a019
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发表时间：
1967
期刊：
影响因子：
--
通讯作者：
Dale E. Battin
中科院分区：
文献类型：
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作者：
A. Winston;J. Sharp;K. Atkins;Dale E. Battin
几种酸酐在二甲氧基乙烷溶液中与三氯乙酸钠发生三氯甲基化反应。三氯甲基化产物以两种互变异构体形式存在，即酮酸或乳糖醇。如果三氯乙酰基和羧基保持在固定的共面，则内酯互变异构体的稳定性相当高，化合物以这种形式结晶。如果基团不是共面的，则酮酸互变异构体是孤立的。在溶液中，化合物处于互变异构平衡状态，可通过光谱检测到两种互变异构体的存在。三氯甲基化产物的产率通常很高，但在副反应特别明显的情况下，产率较低。三氯乙酸钠与醛反应生成三氯甲基甲醇，与乙酰氯反应生成1，1，1-三氯-2-丙酮，与碘甲烷反应生成1，1，1-三氯乙烷。三溴乙酸钠可以用来引入三溴甲基，与酸酐和醛都发生反应。三氟乙酸钠的使用并不成功。三氯乙酸钠和三溴乙酸钠的分解被酸酐的存在强烈地加速。提出了三卤甲基化反应可能有三卤乙酸根参与的可能性，三氯乙酸钠在酸酐存在下的分解是在有机化合物中引入三氯甲基的一种有效的合成方法。2各种酸酐很容易进行加成反应，生成高纯度的三氯甲基酮、酮酸和乳糖醇，通常产率很高。反应非常迅速；在某些情况下，在回流二甲氧基乙烷中只需30分钟就能实现>；70%的产率。偶尔，会导致较低的产率(10-50%)，产品可能会伴随着相当数量的焦油材料。这在一定程度上是由于三氯甲基阴离子从初级产品中提取氢或氯，得到的阴离子可能会发生进一步的反应。这种类型的抽象反应是众所周知的3·4和
Several anhydrides have been subjected to the trichloromethylation reactionusing sodium trichloroacetate in dimethoxyethane solution. The trichloromethylation products exist in either of two tautomeric forms, the keto acid or the lactol. If the trichloroacetyl and carboxyl groups are held in fixed coplanarity, the stability of the lactol tautomer is quite high and the compound crystallizes in that form. If the groups are not held coplanar, then the keto acid tautomer is isolated. In solution the compounds are in tautomeric equilibrium and the pres-ence of two tautomeric forms may be detected spectroscopically. The yields of the trichloromethylation products are generally quite good, but, in cases where side reactions are particularly significant, low yields result. Sodium trichloroacetate reacts with aldehydes to give trichloromethylcarbinols, with acetyl chloride to give 1, 1, 1-trichloro-2-propanone, and with methyl iodide to give 1, 1, 1-trichloroethane. Sodium tribromoacetate may be used to introduce the tribromomethyl group, reaction occurring with both anhydrides and aldehydes. The use of sodium trifluoroacetate has not been successful. The decomposition of sodium trichloro-and tribromoacetate is strongly accelerated by the presence of the anhydride. The possibilitythat the trihalomethylation reaction involves a participation by the trihaloacetate ion is suggested.The decomposition of sodium trichloroacetate in the presence of anhydrides is a useful synthetic method for introducing the trichloromethyl group into organic compounds. 2 A variety of anhydrides readily under-goes the addition reaction to produce trichloromethyl ketones, keto acids, and lactols in high purity, often in excellent yield. The reaction is quite rapid; in certain cases yields of> 70% are realized after only 30 min in refluxing dimethoxyethane. Occasionally, lower yields (10-50%) result, and the product may be accompanied by considerable amounts of tarry material. This is due in part to the abstractionof hydrogen or chlorine from the primary product by the trichloromethyl anion, to give an anion which may undergo further reactions. Abstraction reactions of this type are well known3· 4 and