CO₂与环氧丙烷不对称环加成反应催化体系的设计与研究

【作者】 梁斌；

【导师】 张英菊； 吕小兵；

【作者基本信息】 大连理工大学 ， 应用化学， 2004， 硕士

【摘要】 本文研究了一系列以（R，R）-1，2-环己二胺为手性源衍生的手性Salen配体在CO₂与环氧丙烷不对称环加成反应中的应用。 合成了一系列烷基、卤素和硝基取代的手性Salen配体，分别与Co（Ac）₂形成SalenCo（Ⅱ）配合物，再由不同的酸性基团氧化得到SalenCo（Ⅲ）配合物，原位用于CO₂和环氧丙烷的环加成反应。通过手性气相色谱柱测定了产物碳酸丙烯酯的e．e．值；环氧丙烷的e．e．值经SalenAlEt／n-Bu₄NI催化活化与CO₂环加成转化为碳酸丙烯酯后测定。 在季铵盐（n-Bu₄NY）存在下，SalenCo（Ⅲ）X可以使得CO₂与环氧丙烷的环加成反应在常温下有效进行。n-Bu₄NY中的Y^-对反应速率和产品对映选择性影响较大。以n-Bu₄NCl为助催化剂时，反应速率较低，但对映选择性最好。SalenCo（Ⅲ）X中的轴向基团X—对催化剂的活性及产品的对映选择性也影响较大，空间位阻大的基团有利于不对称诱导。手性Salen配体中苯环上取代基对催化剂的性能也有影响。降低温度会使催化剂活性减弱，但可以促进不对称诱导。在Co、Cr、Mn等金属配合物中，Co配合物的催化效果最佳。更多还原

【Abstract】 A series of chiral Salen ligands derived from (7)-l,2-diaminocyclohexane, were employed in asymmetric cycloaddition of propylene oxide with CO2.A series of alkyl-, halo- and nitro-substituted chiral Salen ligands were prepared. SalenCo( II) complexes derived from the reaction of chiral Salen ligands and Co(OAc)2 were oxidized by different acid groups to form SalenCo (III) complexes, which were employed in asymmetric cycloaddition of propylene oxide with CO2. The e.e. value of propylene carbonate was determined by GC with a chiral chromato-graphic column; and the e.e. value of unreacted propylene oxide was determined after it was transformed into propylene carbonate by reaction with CO2 using SalenAlEt/ n-Bu4NI as catalyst.It was found that the chiral SalenCo(III)X complexes could effectively catalyze the cycloaddation reaction of CO2 with epoxides only in the presence of quaternary ammonium halides(-Bu4NY) at room temperature. The anion Y of n-BuNY in the binary catalyst systems has a great effect on enantiomeric purity and reaction rate. It seems that the use of -Bu4NCl was more beneficial for improving enantiomeric purity of the products, but had a pronounced negative effect on the rate. The axial X-group of chiral SalenCo(III)X complexes also affect enantiomeric purity of the resulted propylene carbonate and propylene oxide. A sterically bulky axial X-group is more beneficial for high enantioselectivity in this reaction. The performance of catalyst is also affected by the substituent on the aromatic rings of chiral Salen ligands. The decrease of reaction temperature is effective for improving enantiomeric purity of the products, but resulting in significant decrease in catalytic activity. Among the synthesized chiral metal-Salen complexes(such as chromium, manganese and cobalt), SalenCo(III)X complexes are more effective in catalytic activity as well as enantioselectivity.更多还原