离子液体在酸催化有机反应和手性分子筛合成中的应用研究

【作者】 吴海虹；

【导师】 何鸣元； 汤杰；

【作者基本信息】 华东师范大学 ， 分析化学， 2004， 博士

【摘要】 室温离子液体是常温下呈液态的熔盐体系。作为挥发性有机溶剂的替代物，室温离子液体正引起广泛关注。本文以离子液体的功能化为出发点，研究了Brφnsted酸性离子液体在某些酸催化反应中的应用，同时，设计、合成了几种手性离子液体，并进行了以手性离子液体为模板剂制备手性分子筛的初步尝试。 （1）醛、酮与醇的缩合反应是羰基保护的通用方法。以Brφnsted酸性离子液体[Hmim]BF₄兼作可循环的反应介质和酸性催化剂，研究了不同结构的羰基化合物分别与新戊二醇、乙二醇和甲醇的缩合反应。结果表明，用新戊二醇在[Hmim]BF₄中保护羰基化合物，试剂与底物等摩尔反应，除一些有位阻的酮外，大多数醛、酮得到几乎定量的转化率，几乎无副反物生成。芳香醛则给出93％～98％转化率的满意结果。 用乙二醇作保护试剂，在同样条件下反应速率有所下降，与新戊二醇相比，醛、酮与乙二醇的反应要达到相似的转化率往往需要更长的反应时间。底物的结构对反应有显著影响，空间位阻和给电子效应对反应不利。 以甲醇作保护剂时，反应相对较难进行，在甲醇6倍过量的条件下，只有脂肪醛和环己酮取得较好的结果。 反应中生成的水不需要被除去，因为反应中生成的水会被[Hmim]BF₄吸收，而大部分缩醛、缩酮产物则不溶于[Hmim]BF₄，可通过简单的重力沉降分离，离子液体仅需简单减压除水后即可循环使用。 （2）以酸性离子液体[Hmim]X（X=Cl、Br、I）兼作卤代试剂、反应介质和酸性催化剂，研究了醇转化为卤代烃的反应。伯醇除某些低沸点底物外，都以高转化率（最高达100％）和高选择性（最高达100％）转化为相应的氯代烃、溴代烃和碘代烃，例如正辛醇、苯甲醇，在[Hmim]X（X=Cl、Br、I）中进行卤代反应得到令人满意的结果，无论氯代、溴代还是碘代得到卤代产物的收率一般都很好华东师范大学化学系01级博士学位论文（95十100%），极少有重排产物及脱水产物被检测出来。仲醇也获得了高转化率，但产物中有脱水副产物生成。由于反应完毕后【H耐m〕X转化为N一甲基咪哇，N-甲基咪哇溶于产物层，因此不能直接分出产物，反应后加入等当量的氢卤酸，分出不溶于离子液体中的卤代烃，除水后〔而im〕X即可再生循环使用。反应实际消耗的是等当量的氢卤酸和醇生成卤代烃和水，是制备伯卤代烃非常有效和清洁的方法。 （3）以L一介)一a一甲基节胺为手性源，设计并合成了系列含一个手性碳的手性离子液体，并以此作为手性模板剂进行了手性分子筛的合成尝试。以L一C)一N一（Q一甲基节基）一N，N一二甲基一十六烷基滨化钱为模板剂在酸性（盐酸）条件下合成分子筛，得到有序结构，其XRD图谱与MCM一41标准图谱相似。更多还原

【Abstract】 Room temperature ionic liquids are molten salts that being liquids at normal temperature. As a replacer of versatile organic solvents, room temperature ionic liquids are attracting scientist’s more attention. In this dissertation, the application of Bransted acidic ionic liquid in some reaction, which normally catalyzed by acid, was investigated. Moreover, several chiral ionic liquids, which were further served as structure directing agent for preparation of chiral sieves, were designed and synthesized.(1) Condensation of aldehydes or ketones with alcohols is one of the most common methods for protecting carbonyls. In this thesis, the condensation of different carbonyls with neopentyl glycol, ethylene glycol and methanol, respectively, was studied with Bransted acidic ionic liquid as recyclable medium as well as acidic catalyst. Using neopentyl glycol as protecting reagents, the results showed that most of the aldehydes or ketones gave almost quantitative conversions in [Hmim]BF4 except for the ketones with big steric hindrance. Satisfactory conversions of 93% ~ 98% for aromatic aldehydes were obtained.Using ethylene glycol as protecting reagents, the reaction rates slightly decreased under the same reaction conditions. Longer reaction time was required to obtain similar conversions and selectivities compared with neopentyl glycol. The steric hindrance and electron-donating effect were unfavorable to the condensation reactions.The protection with methanol was difficult to proceed. Better results only for aliphatic aldehydes and cyclohexanone were obtained while using a higher proportion of methanol (molar ratio 1:6).The water produced in the reactions did not need to be removed during the reaction because [Hmim]BF4 was miscible with water while the acetals or ketals were immiscible with [Hmim]BF4. Hence the product could be separated conveniently bydecanting. The ionic liquid [Hmim]BF4 could be easily recycled. After reaction, [Hmim]BF4 was readily separated and reused after drying in vacuum.(2) The conversion of alcohols to alkyl halides was investigated using acidic ionic liquid [Hmim]X as halogenating agent, acidic catalyst as well as medium. The reactions of primary alcohols gave very satisfactory conversions and selectivities except for the substrates with lower boiling point,such as n-octanol and benzyl alcohol. They obtained the corresponding halides with almost quantitative yields(95%-100%) .The secondary alcohols also gave the corresponding halides with excellent conversions, however, the by-products of dehydration were detected. [Hmim]X was transformed into methylimidazole after the reaction. The methylimidazole was dissolved in the products halide, so the product could not be isolated directly. After the reaction, the insoluble halide could be easily separated by addition of equivalent of halogen acid, and the ionic liquid [Hmim]X could be regenerated conveniently by removal of water. Hence, for the whole process, the reaction consumed equivalent of halogen acid and alcohol to produce halide and water. The procedure is very practive for the preparation of primary halides.(3) Series of chiral ionic liquid, which contained one chiral carbon, was designed and synthesized using L-(-)- a -methylbenzylamine as the starting substrate. The attempts for preparing chiral molecular sieves were made with the chiral ionic liquid L-(-)- a -methylbenzyl-N,N-dimethylbromocetylquaternary ammonium salt as structure directing agent. We got a product which construction as that of MCM-41.更多还原