双官能团离子液体[Promim]^+[CF_3CO_2]^-支撑不对称Aldol反应的密度泛函理论研究(英文)  

DFT Study on the Bifunctional Ionic Liquid [Promim]^+ [CF_3CO_2]^--Supported Asymmetric Aldol Reaction

作　　者：张金生[1] 陈卓[1] 谢辉[1] 申婧[1] 许亮[1] 

机构地区：[1]贵州师范大学化学与材料科学学院,贵阳550001

出　　处：《西南大学学报（自然科学版）》2011年第7期41-49,共9页Journal of Southwest University(Natural Science Edition)

基　　金：贵州省科学技术基金资助项目(黔科合J字[2009]2241号);国家自然科学基金资助项目(20862004);贵州师范大学博士科研启动基金资助项目

摘　　要：用密度泛函理论B3LYP方法对双官能团离子液体[Promim]+[CF3CO2]-支撑丙酮与邻-硝基苯甲醛不对称aldol反应进行了研究.结果表明,该离子液体的脯胺酸和咪唑基团一起对反应产生催化作用.整个反应包括:丙酮的羰基与脯胺酸基团的胺基间的亲核加成反应,咪唑2-位氢参与的脱水反应生成亚胺IM1-2,丙酮甲基脱氢反应生成烯胺I M1-3,苯甲醛与烯胺的亲核加成反应,水加成反应和催化剂再生反应.第一步骤是速率控制步骤,产物羟基位碳原子的手性在苯甲醛与烯胺的亲核加成反应中产生.另外,在咪唑环2-位氢参与的脱水反应中生成的水分子辅助丙酮甲基脱去α-氢生成烯胺.苯甲醛邻位吸电子基团能降低醛基碳原子的电子密度,增强醛基碳原子的亲电性,从而增强反应物活性.离子液体[Promi m]+[CF3CO2]-产生的溶剂化效应使反应势垒降低(除开催化剂再生步骤).By using the B3LYP method of the density functional theory（DFT）,the bifunctional ionic liquid（IL） [Promim]＋ [CF3CO2]--supported asymmetric aldol reaction between ketone and o-nitrobenzaldehyde is theoretically studied.The results demonstrate that bifunctional proline and imidazole fragments of the IL coordinate to catalyze the reactions.The overall reactions are initiated by a nucleophilic addition reaction of the proline fragment with the carbonyl group of ketone,and subsequently go through a dehydration reaction,a dehydrogenation,a nucleophilic addition of enamine with aldehyde,a hydration reaction and a regeneration of the catalyst.The first step is rate-controlling,and the chiral carbon center is generated in the enamine nucleophilic addition with the aldehyde.It is a new finding that the 2-position hydrogen of the imidazole fragment takes part in the dehydration reaction leading to an imine onium IM1-2.Moreover,a water molecule acts as a hydrogen shuttle to transport a hydrogen atom from methyl of ketone to carbonyl-oxygen of aldehyde fragment.The electron-withdrawing inductive effect of ortho-nitro-group in phenyl decreases the electron density of the carbonyl carbon and increases its electrophilic ability,thus promoting the nucleophilic addition reaction of the enamine with aldehyde.On the whole,the ionic liquid of [Promim]＋ [CF3CO2]- decreases the reaction barriers excluding the last steps.

关 键 词：双官能团离子液体 不对称ALDOL反应 密度泛函理论 亲核加成 氢转移 

分 类 号：O643.12[理学—物理化学]