Diastereodivergent Asymmetric 1,4-Addition of Oxindoles to Nitroolefins by Using Polyfunctional Nickel-Hydrogen-Bond-Azolium Catalysts
作者:Melanie Mechler、René Peters
DOI:10.1002/anie.201502930
日期:2015.8.24
groups, and an axially chiral bisimidazolium entity participate in the stereocontrol of the direct 1,4‐addition of oxindoles to nitroolefins. Both epimers of the 1,4‐adduct are accessible in excess on demand by changes to the ligand constitution and configuration. As the products have been reported to be valuable precursors to indole alkaloids, this method should allow access to their epimeric derivatives
非对映异构性是催化不对称合成的挑战。对于许多反应类型,固有地优选一种非对映异构体的生成,而其他非对映异构体不能高效地直接获得并且需要circuit回合成方法。通过催化剂覆盖固有的偏好,需要控制两个反应伙伴的空间位置。我们报告了一种新型的多官能催化剂类型,其中Ni II-双(苯氧基亚胺)单元,游离羟基和轴向手性双咪唑鎓实体参与将吲哚直接1,4-加成到硝基烯烃的立体控制。1,4-加合物的两个差向异构体可通过改变配体的组成和构型按需获得。由于据报道该产品是吲哚生物碱的有价值的前体,因此该方法应允许获得其差向异构衍生物。