1394920-56-9Relevant articles and documents
Diastereodivergent Asymmetric 1,4-Addition of Oxindoles to Nitroolefins by Using Polyfunctional Nickel-Hydrogen-Bond-Azolium Catalysts
Mechler, Melanie,Peters, Ren
supporting information, p. 10303 - 10307 (2015/09/01)
Diastereodivergency is a challenge for catalytic asymmetric synthesis. For many reaction types, the generation of one diastereomer is inherently preferred, while the other diastereomers are not directly accessible with high efficiency and require circuitous synthetic approaches. Overwriting the inherent preference by means of a catalyst requires control over the spatial positions of both reaction partners. We report a novel polyfunctional catalyst type in which a NiII-bis(phenoxyimine) unit, free hydroxy 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.
Squaramide-catalyzed diastereo- and enantioselective Michael addition of 3-substituted oxindoles to nitroalkenes
Yang, Wen,Wang, Jingsi,Du, Da-Ming
experimental part, p. 972 - 980 (2012/09/22)
An efficient diastereo- and enantioselective Michael addition of 3-substituted oxindoles onto nitroalkenes catalyzed by a bifunctional chiral squaramide catalyst has been developed. This organocatalytic reaction with 2 mol % of catalyst proceeded smoothly
