【作者】 于红杰；

【导师】 兰支利；

【作者基本信息】 湖南师范大学 ， 有机化学， 2009， 硕士

【摘要】 微反应器模拟细胞空腔及酶的催化功能是当前化学研究中的一个前沿领域,环糊精作为一种重要的微反应器越来越受到人们的重视。它是由D-（+）葡萄糖以α-1,4糖苷键结合而形成的一类环状低聚糖（n=6,α;n=7,β;n=8,γ）,形似中空的圆筒,腔内是醚键和碳氢键,具疏水性,腔外含有羟基,具亲水性。环糊精能与多种无机或有机分子在水溶液中发生包合作用,其手性微环境能够催化诱导不对称化学反应,同时利用其在水中的溶解性,充当逆相转移催化剂,提高反应的选择性。环糊精微反应器中发生的反应以水为介质,避免了有机溶剂和金属催化剂的使用,操作方便,反应条件温和,符合绿色化学的发展要求。本文选择了还原反应、氧化反应及其缩合反应为探针反应,研究了这些反应在环糊精微反应器中的反应规律,获得了以下几个方面的结果:1.系统考察了环糊精微反应器存在下,苯乙酮衍生物中取代基团对不对称还原反应的影响。研究中发现当苯乙酮上连有取代基团且在低温条件下进行不对称还原反应时,对映体选择性得到提高,产物醇的绝对构型与取代基团的位置有关,苯乙酮及其间位、对位衍生物还原产物绝对构型为S型,邻位衍生物所得产物为R型。苯乙酮衍生物的对映体选择性是取代基团的大小、氢键作用、空间位阻等协同作用的结果。根据取代基团的性质以及取代位置,提出了底物在β-环糊精微反应器内中的可能定位机理。2.在NaBH₄还原胺/酮/环糊精形成的三元包合物体系中,考察了胺的类型,β-环糊精、苯乙酮和环己胺的摩尔比以及反应温度对苯乙酮不对称还原反应的影响。实验结果表明,较之酮/环糊精形成的二元包合物体系,加入环己胺,产物醇的绝对构型发生了翻转（从S型变为R型）,当β-环糊精、苯乙酮和环己胺的摩尔比为2:1:3,反应温度为-5℃,R（+）-1-苯乙醇对映体过量率达到20%;而没有环己胺,S（-）-1-苯乙醇对映体过量率仅为6%。3.查尔酮及其衍生物是一类重要的有机中间体,常规的合成方法产率一般不高,反应条件苛刻。在此我们研究了以水为反应溶剂,以环糊精逆相转移催化绿色无污染合成查尔酮的新方法,产率最高可达90%。该方法避免了使用强碱,反应体系易与产物分离,催化剂可以循环使用。4.研究了环糊精微反应器中的苯甲醇氧化制备苯甲醛的反应。实验结果表明,环糊精在此反应中充当了逆相转移催化剂的作用,通过一锅法高选择性地合成了苯甲醛,具有反应条件温和、无环境污染、操作简单、用水作为溶剂、环糊精可以循环使用等优点。在反应温度为25℃,反应时间为10 h,β-环糊精、苯甲醇、NBS的摩尔比为2:1:2时,苯甲醛的产率可达83.7%。更多还原

【Abstract】 It’s a new topic for chemists to research on modeling the function of cell’s environment and enzymes via microreactors.As an important microreactor,cyclodextrin（CD） is attracting more and more attention. Cyclodextrins are a class of cyclic oligosaccharide molecules normally comprised of six（α）,seven（β） or eight（γ）α-1,4 linked D（+）-glucopyranose unite,in which the interior surface of the cavity is hydrophobic and the external surface is hydrophilic.They are well known for their ability to form inclusion complexes with a wide variety of guest molecules ranging from organic molecules to inorganic compounds and ions in aqueous solution.Cyclodextrins can be used as chiral microreactors because of their ability of asymmetric induced chemical reactions.Cyclodextrins are also efficient inverse phase transfer catalysts（IPTC） for they are soluble in water and can form inclusion complexs with hydrophobic organic compounds.These processes occur in water,which is attractive as an environmentally benign solvent,which avoids the environmental pollution from organic solvents and metal catalysts.The reaction condition is mild and the operation is convenient and simple.In this thesis,we investigated the behavior of asymmetric reduction,oxidation, condensation in microreactor of cyclodextrins,the research results are as follows:1.Effects of substuent groups in the presence of microreactors of cyclodextrins on asymmetric reduction of acetophenone derivatives have been studied.The results indicated that substituent groups and low reaction temperature improved enantioselectivity for this asymmetric reaction.Absolute configuration of the resulting alcohols are depending upon the positions of substuent groups,preponderant absolute configuration of acetophenone and its meta- and para-derivatives was the S while the prevailing absolute configuration was the R in the case of the orth-derivatives.Effects of enantioselectivity of substituted acetophenones were due to the combination of bulkiness of substituent groups,hydrogen bonding,space steric hindrance and so on.In addition,preferential orientations of the substrate included inside the microreactor ofβ-cyclodextrin are suggested from above results.2.While the three-component inclusion complex is asymmetric reduced by the NaBH₄,the effect factors on asymmetric reduction of the acetophenone such as the kind of amides,molar ratio of theβ-Cyclodextrin/ketone/anime,temperature have been examine.Compared with binary system,the results indicated that cyclohexanamine enhanced chiral induction and inverted alcohol configuration.R（+）-1-phenylethanol was produced in 20%enantiometric excess for a molar ratioβ-CD:acetophenone:cyclohexanamine of 2:1:3,the reaction temperature is-5℃;the S（-） enantiomer in 6%enantiometric excess in the absence of cyclohexanamine.3.Chalcone and its derivatives are important organic intermediates. A new green method was studied for synthesis of Chalcones using microreactor of cyclodextrin as the inverse phase transfer catalysts and refluxed in water,the isolated yield was up to 90%.The method precludes the use of either strong base and product can be easily separated.The catalyst can be recycled with no pollution to the environment.4.Benzyl alcohol was oxidized to benzaldehyde under a mild condition in microreactor of cyclodextrins.The results showed that microreactor of cyclodextrins can be regarded as inverse efficient phase transfer catalysts for the oxidation of benzyl alcohol,this method is a direct one-pot synthesis under mild conditions,without pollution to the environment,the experimental steps are simple,cyclodextrins can be recovered and reused without loss of activity.Yield of benzaldehyde was up to 83.7%when the reaction temperature is 25℃,reaction time is 10 h, the molar ratio of theβ-cyclodextrin,benzyl Alcohol and NBS is 2:1:1.更多还原