Catalytic asymmetric cycloadditions and cascade cyclizations are a major focus for the enantioselective construction of chiral carbo- and heterocycles. A number of chiral Lewis acids and organocatalysts have been designed for such reactions. The development of broadly applicable catalysts bearing novel chiral backbones to meet the demands of various applications is an ongoing challenge. Approximately 10 years ago, we introduced a group of conformationally flexible C₂-symmetric N,N′-dioxide amide compounds, which represent a new class of privileged ligands. The coordination of the four oxygens of a chiral N,N′-dioxide around a central metal generates an octahedral tricyclometalated Lewis acid catalyst that can carry out various enantioselective reactions. In this Account, we summarize our recent studies on asymmetric cycloadditions between various dienophiles and dienes, dipoles and dipolarophiles, and cascade cyclizations catalyzed by chiral N,N′-dioxide–metal complexes. In principle, these unique chiral catalysts lower the LUMO energy of electron-deficient 2π components or heterodienes by coordination with the functional groups via various binding modes.

中文翻译：

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N，N'-二氧化物-手性金属配合物催化不对称环加成反应和环化反应

催化不对称环加成反应和级联环化反应是手性碳环和杂环的对映选择性构建的主要重点。已经设计出许多手性路易斯酸和有机催化剂用于这种反应。带有新型手性主链以满足各种应用需求的广泛应用的催化剂的开发是一个持续的挑战。大约10年前，我们引入了一组构象灵活的C ₂对称N，N'-二氧化物酰胺化合物，它们代表一类新的特权配体。手性N，N的四个氧的配位中心金属周围的'-二氧化物生成八面体三环金属化的路易斯酸催化剂，该催化剂可以进行各种对映选择性反应。在这个报告中，我们总结了我们最近对各种双烯亲二烯和二烯，偶极和双亲亲烯之间的不对称环加成以及手性N，N'-二氧化物-金属络合物催化的级联环化的研究。原则上，这些独特的手性催化剂通过各种键合方式与官能团配位，从而降低了缺电子的2π组分或杂二烯的LUMO能量。