Key laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu, 610064, China.
Angew Chem Int Ed Engl. 2022 Nov 2;61(44):e202211596. doi: 10.1002/anie.202211596. Epub 2022 Oct 6.
An efficient catalytic asymmetric [2+2] cycloaddition of allenyl imide and mono- or disubstituted alkenes is disclosed. The key feature of this method is the use of bidentate allenyl imide and weakly activated and less steric hindered alkene pair by utilizing chiral magnesium(II) complex of N,N'-dioxide, which could provide through-space dispersion interactions to orientate the arrangement of the alkene. This protocol allows the generation of a series of axially chiral cyclobutenes and four-membered ring-containing spirocycles (80 examples) in high yield (up to 99 %) with excellent enantioselectivity (up to >99 % ee), and the late-stage modification of biologically active molecules as well. Experimental studies and DFT calculations revealed that this [2+2] cycloaddition proceeded via a stepwise mechanism involving a short-lived zwitterionic intermediate. The π-π interaction between the alkenes and the amide moiety in the ligand was crucial for the enantiocontrol.
本文报道了一种高效的手性催化 Allenyl 亚胺与单取代或双取代烯烃的不对称 [2+2]环加成反应。该方法的关键特点是使用双齿 Allenyl 亚胺和弱活化、位阻较小的烯烃对，通过利用手性镁（II）配合物的 N，N'-二氧化物，从而提供空间分散相互作用，以定向烯烃的排列。该方案允许在高收率（高达 99%）和优异的对映选择性（高达>99%ee）下生成一系列轴手性环丁烯和含四元环的螺环化合物（80 个实例），并能对生物活性分子进行后期修饰。实验研究和 DFT 计算表明，该 [2+2]环加成反应通过涉及短寿命两性离子中间体的分步机制进行。烯烃与配体中亚酰胺部分之间的π-π相互作用对于对映体控制至关重要。
