【作者】 赵成艳； 傅爱萍； 田昌可； 李洪亮； 段云波；

【Author】 Cheng-Yan Zhao;Ai-Ping Fu;Chang-Ke Tian;Hong-Liang Li;Yun-Bo Duan;Laboratory of New Fiber Materials and Modern Textile,the Growing Base for State Key Laboratory,Qingdao University;

【机构】 青岛大学纤维新材料与现代纺织国家重点实验室培育基地；

【摘要】 以α,α-双烷基取代的醛为供体的aldol反应由于可以作为潜在的季碳中心的构建方法而备受关注,但该类特殊供体在反应过程中表现出的不同的化学选择性和立体选择性又使合成过程面临巨大的挑战1,2。因此对其反应机理进行研究可为新型催化剂的研发以及获得不同立体构型的产物提供指导。本文采用M06-2X方法结合SMD溶剂模型考察了脯氨酸及其衍生物催化的以异丁醛为供体,对硝基苯甲醛为受体的aldol反应的立体控制步骤,计算得到的主产物与ee值与实验结果非常吻合。由于反应过程中的受体对硝基苯甲醛的面选择性与以往报道的异丁醛为供体的aldol反应的选择性根源的解释相反2,我们进一步采用AIM和NBO理论对不同催化过程过渡态进行分析,确认了不同受体醛的面选择性的根源。更多还原

【Abstract】 Direct access to products with quaternary carbon atoms from α,α-dialkyl donors has draw great attention in asymmetric organic chemistry although it is challenging to carry out the process using those kinds of aldehydes as nucleophilic aldol partners. The enantioselectivities in proline and its derivative-catalyzed asymmetric aldol reactions between isobutyraldehyde and paranitrobenzaldehyde have been investigated by performing M06-2X calculations in combination with SMD solvation model. The predicted ee values are in good agreement with the experimental observations. However, the facial selectivity of the aldol acceptor in the more favorable TS is in contrast to the previous explaination for the reactions involving isobutyraldehyde as the donor e.g. minimization of the gauch interactions around the forming C-C bond. The AIM and NBO analyses are employed to explain the difference of the facial-selectivity between different aldol acceptors.更多还原