Institute of Drug Synthesis and Pharmaceutical Process, School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou 510006, China.
Chirality. 2012 Mar;24(3):232-8. doi: 10.1002/chir.21987. Epub 2012 Jan 25.
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.
一系列手性吡咯烷磺酰胺被制备出来,并被用作酮与硝基烯烃共轭加成的催化剂。苯甲酸被确定为该转化最有效的添加剂。在无溶剂条件下,环己酮与β-芳基硝基乙烯的反应可获得优异的对映选择性、非对映选择性和收率。β-异丙基硝基乙烯也适用,延长反应时间后可获得具有优异对映选择性的产物。不同侧链的吡咯烷磺酰胺有机催化剂的催化行为比较表明,对映选择性主要受手性吡咯烷单元控制,而侧链上额外的手性中心的影响可以忽略不计。氢键相互作用被认为在硝基烯烃的活化和有序过渡态的形成中起着关键作用。