title: Enantioselective conjugate addition of ketones to nitroalkenes catalyzed by pyrrolidine-sulfamides.
abstract: A series of chiral pyrrolidine-sulfamides were prepared and examined as the catalysts for conjugate addition of ketones to nitroalkenes. Benzoic acid was identified as the most efficient additives for the transformation. Excellent enantioselectivities, diastereoselectivities, and yields were achieved for the reaction of cyclohexanone with β-aryl nitroethylenes under solvent free conditions. β-Isopropyl nitroethylene is also applicable and the product could be obtained with excellent enantioselectivity after extended reaction time. A comparison of the catalytic behaviors of pyrrolidine-sulfamide organocatalysts with different side chains demonstrates that the enantioselectivity is mainly controlled by the chiral pyrrolidine unit and the additional chiral center at the side chain exerts neglectable effects. The H-bonding interaction between the sulfamide and the nitro group is proposed to be crucial for the activation of the nitroalkene and the constitution of well-organized transition state.
authors.affiliation: Institute of Drug Synthesis and Pharmaceutical Process, School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou 510006, China.
authors.forename: Jinjia
authors.initials: J
authors.lastname: Wang
authors.forename: Jinhua
authors.initials: J
authors.lastname: Lao
authors.forename: Quansheng
authors.initials: Q
authors.lastname: Du
authors.forename: Shaozhen
authors.initials: S
authors.lastname: Nie
authors.forename: Zhipeng
authors.initials: Z
authors.lastname: Hu
authors.forename: Ming
authors.initials: M
authors.lastname: Yan
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D000577:Amides / Q000737:chemistry*; D002384:Catalysis; D007659:Ketones / Q000737:chemistry*; D009574:Nitro Compounds / Q000737:chemistry*; D011759:Pyrrolidines / Q000737:chemistry*; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D000475:Alkenes; D000577:Amides; D007659:Ketones; D009574:Nitro Compounds; D011759:Pyrrolidines; C032519:pyrrolidine