REACTION OF ISOBUTYLENE CARBONATE WITH SECONDARY AMINES. OBSERVATION OF KINETIC AND THERMODYNAMIC PRODUCTS
REACTION OF ISOBUTYLENE CARBONATE WITH SECONDARY AMINES. OBSERVATION OF KINETIC AND THERMODYNAMIC PRODUCTS
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碳酸异丁烯与仲胺的反应。
DOI：
10.1002/chin.198106172
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发表时间：
1980
期刊：
影响因子：
--
通讯作者：
D. E. Kuhla
中科院分区：
文献类型：
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作者：
C. Sklavounos;I. M. Goldman;D. E. Kuhla
不对称环状碳酸酯已被证明与胺反应，得到预期的异构体氨基甲酸酯的混合物。Katzhendler及其同事注意到取代基的极性和体积等因素对氨基甲酸酯异构体分布比例的影响，但排除了反应条件下产物之间热力学平衡的可能性。2我们希望报道碳酸异丁烯酯（1，方案I）与仲胺的反应以动力学产物混合物（2和3）的初始形成进行，所述动力学产物混合物实际上然后经历平衡成为几乎仅包含3的热力学产物混合物。碳酸异丁酯（1）与吗啉在120 ℃下的反应如表I所示。通过使用NMR测定来跟踪起始材料的消失速率和产物2b和3b的出现，观察到在反应的早期阶段形成了由超过3b的过量2b组成的动力学产物混合物。当反应进行到完全时，3b/2b比率增加到大于97：3的热力学平衡值。当相同的反应在20 ℃下进行36天时，得到3b/2b的约50 ∶ 50的混合物（也含有20%的原料）。通过柱色谱法从该混合物中分离化合物2b，并且当在室温下在D2 O中用过量吗啉处理时，显示以98%产率得到3b。因此，发现在与Katzhendler所采用的类似的纯反应条件或水反应条件下，产物氨基甲酸酯都发生了平衡。2在极性质子溶剂中，1的氨解和2向3的转化似乎都是最容易的。例如，在水3中，反应在室温下在30分钟内完成（1完全消耗，3/2比例约为98：2），而在乙腈、Me 2SO或过量胺（纯）中，完成需要相当长的时间或更高的温度。
Unsymmetrical cycliccarbonates have been reported1, 2 to react with amines to give mixtures of the expected isomeric carbamates. Katzhendler and co-workers noted the effects of factors such as polarity and bulk of sub-stituents on carbamate isomer distribution ratios but ex-cluded the possibility of thermodynamic equilibration between the products under the reaction conditions. 2 We wish to report that the reaction of isobutylene carbonate (1, Scheme I) with secondary amines proceeds with initial formation of a kinetic product mixture (2 and 3) which indeed then undergoes equilibration to the thermodynamic product mixture comprised almost exclusively of 3. The reaction of isobutylene carbonate (1) with mor-pholine at 120 C is illustrative as summarized in Table I. By use of a NMR assay to follow the rate of disappearance of starting materials and the appearance of products 2b and 3b, it was observed that a kinetic product mixture consisting of an excess of 2b over 3b was formed at the early stages of thereaction. As the reaction pro-ceeded toward completion the 3b/2b ratio increased to the thermodynamic equilibrium value of greater than 97: 3. When the same reaction was run at 20 C for 36 days, an approximately 50: 50 mixture of 3b/2b was obtained (also containing 20% starting materials). Compound 2b was isolated from this mixture by column chromatography and shown to give 3b in 98% yield when treated at room tem-perature in D20 with excess morpholine. Equilibration of the product carbamates is therefore found to occur under both neat or aqueous reactionconditions similar tothose employed by Katzhendler. 2 Both the aminolysis of 1 and the transformation of 2 to 3 appear to be most facile in polar protic solvents. For instance, in water3 the reaction is complete (1 completely consumed, 3/2 ratio of approx-imately 98: 2) within 30 min at room temperature while in acetonitrile, Me2SO, or excess amine (neat), considerably longer times or higher temperatures are necessary for completion.