Readily available chiral thioureas derived from cyclohexane-1,2-diamine were prepared and found to be highly effective organocatalysts for the conjugate addition of aldehydes and ketones to nitroalkenes. Excellent enantioselectivities and yields were obtained for a variety of aryl and heteroaryl nitroalkenes. The base additives are essential for good yields and excellent enantioselectivities in this
Magnetic Nanoparticles-Supported Chiral Catalyst with an Imidazolium Ionic Moiety: An Efficient and Recyclable Catalyst for Asymmetric Michael and Aldol Reactions
only in the enantioselective Michael addition but also in the asymmetric aldol condensation to afford good to excellent yields (70–94%) and satisfactory stereoselectivity (ee: 92–100%, dr: 91:9–99:1).The role of the ionic moiety was verified by comparison of the catalyst with an ionic moiety‐free counterpart. The heterogeneous catalyst was easily separated and recovered using external magnetic force
to 98%) with high to excellent enantioselectivities (up to 99% ee). Chiral primary amine–squaramides have not been extensively studied to date in the field of organocatalysis. In this paper, novel chiralsquaramidesderived from natural product stevioside were developed. Both enantiomers of a series of γ-nitroaldehydes were generated by using these squaramidecatalysts for the Michael addition reaction
Highly Enantioselective Michael Additions of Isobutyraldehyde to Nitroalkenes Promoted by Amphiphilic Bifunctional Primary Amine-Thioureas in Organic or Aqueous Medium
isobutyraldehyde and nitroalkenes. The chiral thiourea 1a furnished S enantiomers, whereas 1b afforded R enantiomers, both with high yields (up to 92 %) and high to excellent enantioselectivities (up to 98 %). Furthermore, the reactions proceeded smoothly both in organic solvents and in water under mild conditions.
设计并合成了一类新的基于拜耳烷支架的手性两亲双功能硫脲,每个硫脲都含有伯氨基,从容易获得的天然产物异甜菊醇中合成。硫脲被证明可有效催化异丁醛和硝基烯烃之间的不对称迈克尔加成。手性硫脲 1a 提供 S 对映异构体,而 1b 提供 R 对映异构体,两者均具有高产率(高达 92 %)和高至极好的对映选择性(高达 98 %)。此外,反应在温和条件下在有机溶剂和水中均顺利进行。