Department of Chemistry, Sungkyunkwan University, Suwon 16419, Korea.
Org Lett. 2019 Sep 6;21(17):6715-6719. doi: 10.1021/acs.orglett.9b02320. Epub 2019 Aug 16.
Water enables the highly challenging enantioselective Michael addition of sterically congested β-trifluoromethyl-β-aryl- or -alkyl-substituted nitroolefins with dithiomalonates. Under on-water conditions, the reaction rates were remarkably accelerated as a result of enforced hydrophobic interactions between catalysts and reactants. Takemoto-type thiourea catalysts are very effective for this transformation, affording highly enantioenriched Michael adducts that provide simple access to chiral γ-aminobutyric acid (GABA) analogues with a β-trifluoromethylated quaternary stereocenter.
水促进了位阻较大的β-三氟甲基-β-芳基或-β-烷基取代的硝基烯烃与二硫代丙二酸酯的高度立体选择性迈克尔加成。在水相条件下，由于催化剂和反应物之间强制的疏水相互作用，反应速率显著加快。Takemoto 型硫脲催化剂对此转化非常有效，得到高对映体富集的迈克尔加成产物，为具有β-三氟甲基化的季立体中心的手性γ-氨基丁酸（GABA）类似物提供了简单的途径。
