1440200-03-2Relevant academic research and scientific papers
Highly enantioselective Michael addition of pyrazolin-5-ones to nitroolefins catalyzed by cinchona alkaloid derived 4-methylbenzoylthioureas
Yang, Mengchen,Zhang, Min,Wang, Zhenyu,Tang, Li,Chen, Wenbin,Ban, Shurong,Li, Qingshan
supporting information, p. 1096 - 1104 (2018/08/11)
Cinchona alkaloid-derived 4-methyl/nitro benzoylthioureas were synthesized, which smoothly catalyzed the asymmetric Michael addition of pyrazolin-5-ones to nitroolefins. The results showed that electronic effects of substituents in the benzene ring of benzoylthioureas have subtle influences on their catalytic abilities and electron donating methyl group is favored than electron withdrawing nitro group. Preliminary Hartree-Fock calculations revealed that in the catalytic cycle, hydrogen bond energies of the complex formed with 4-methylbenzoylthioureas are about 0.19 to 1.56?kcal/mol higher than with the corresponding 4-nitrobenzoylthioureas. 4-Methylbenzoylthioureas were identified as the most effective catalysts that promoted asymmetric Michael addition of pyrazolin-5-ones to nitroolefins to give the S- or R-products with high enantioselectivities.
Asymmetric cooperative catalysis in the conjugate addition of pyrazolones to nitroolefins and subsequent dearomative chlorination
Zhang, Kefeng,Li, Feng,Nie, Jing,Ma, Junan
, p. 265 - 275 (2014/03/21)
Over the past decade many bifunctional amine-thioureas have been developed as active metal-free organocatalysts. Cooperative catalysis of these amino-thioureas allows high reaction rates and excellent transfer of stereochemical information. Despite these impressive advances, the design of new high-performance catalysts for applications in asymmetric catalytic reactions is of ongoing interest in organic chemistry. Herein we describe a cooperative catalyst system consisting of a chiral aminethiourea and an achiral organic acid that promotes the conjugate addition of 4-nonsubstituted pyrazolones to nitroolefins and subsequent dearomative chlorination. The corresponding adducts and the subsequent products were obtained in high to excellent yields (up to 99%) and high stereoselectivities (up to 99/1 dr, 98% ee) under mild reaction conditions. These transformations provide an easy access to enantio-enriched pyrazole derivatives, which could possess potential pharmaceutical activity.
Squaramide-catalysed enantioselective Michael addition of pyrazolin-5-ones to nitroalkenes
Li, Jun-Hua,Du, Da-Ming
, p. 6215 - 6223 (2013/09/12)
An efficient chiral squaramide-catalysed enantioselective Michael addition of pyrazolin-5-ones to nitroalkenes has been developed. This reaction afforded the chiral pyrazol-3-ol derivatives in high to excellent yields (up to >99%) with high enantioselecti
Highly diastereo- and enantioselective organocatalytic one-pot sequential 1,4-addition/dearomative-fluorination transformation
Li, Feng,Sun, Long,Teng, Yuou,Yu, Peng,Zhao, John Cong-Gui,Ma, Jun-An
supporting information, p. 14255 - 14260 (2013/01/15)
Fluorination: A wide range of nitroolefins and pyrazol-5-ones undergo a sequential 1,4-addition/dearomative-fluorination transformation when treated with a catalytic amount of a tertiary-amine-thiourea compound and the terminal electrophile, N-fluorobenzenesulfonimide, to give fluorinated products in 72-95 % yield with up to 99:1 d.r. and 98 % ee. Notably, these products contain adjacent tertiary and α-fluoro quaternary stereocenters (see scheme). Copyright
