Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064, P.R. China.
Chemistry. 2013 Apr 15;19(16):5134-40. doi: 10.1002/chem.201203891. Epub 2013 Feb 27.
We demonstrated an asymmetric 1,3-dipolar cycloaddition of azomethine betaines with alkylidene malonates by using a chiral N,N'-dioxide-Ni(II) complex as a catalyst. Both aromatic- and aliphatic-substituted alkylidene malonates were found to be suitable for the reaction. A range of trans-pyrazolone derivatives was exclusively obtained with excellent yields (up to 99% yield) and good enantioselectivities (up to 97% ee) under mild reaction conditions. The reaction could be carried out on a gram scale with the good results being maintained. Control experiments were performed to elucidate the specific diastereoselectivity of the reaction. The formation of single trans isomers was dominated by secondary orbital interactions between the ester groups of the dipolarophile and the azomethine imine. On the basis of the experimental results and previous reports, a possible catalytic model was assumed.
我们展示了一种不对称的 1,3-偶极环加成反应，使用手性 N,N'-二氧化氮-镍（II）配合物作为催化剂，使亚胺盐与亚甲基丙二酸酯反应。发现芳香族和脂肪族取代的亚甲基丙二酸酯都适合该反应。在温和的反应条件下，以高收率（高达 99%的收率）和良好的对映选择性（高达 97%的 ee）获得了一系列反式吡唑啉酮衍生物。反应可以在克级规模上进行，并且保持良好的结果。进行了控制实验以阐明反应的特定非对映选择性。单反式异构体的形成主要由亲偶极体的酯基与亚胺亚胺之间的二级轨道相互作用决定。根据实验结果和以前的报道，假设了一个可能的催化模型。
