Chiral amine-squaramide is a kind of effective hydrogen bond donor bifunctional catalyst to promote many asymmetric transformations. In this paper, novel chiral tertiary amine-squaramide derived from the natural product of the stevioside was developed and applied into the asymmetric Michaeladdition of acetylacetone to nitroolefins. This asymmetric reaction performed well, and a series of enantiomerically
Doubly stereocontrolled asymmetric Michael addition of acetylacetone to nitroolefins promoted by an isosteviol-derived bifunctional thiourea
作者:Zhi-wei Ma、Yu-xia Liu、Li-juan Huo、Xiang Gao、Jing-chao Tao
DOI:10.1016/j.tetasy.2012.03.020
日期:2012.4
A novel class of chiral bifunctionalthioureas bearing a chiral lipophilic beyerane scaffold and a tertiary amino group was designed and prepared. The thioureas were proven to be effective for catalyzing the doubly stereocontrolled asymmetricMichaeladdition between acetylacetone and nitroolefins. The corresponding adducts were obtained in high yields (up to 95%) and with good to excellent enantioselectivities
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。