Highly enantioselective Michael addition of pyrazolin-5-ones to nitroolefins catalyzed by cinchona alkaloid derived 4-methylbenzoylthioureas
作者:Mengchen Yang、Min Zhang、Zhenyu Wang、Li Tang、Wenbin Chen、Shurong Ban、Qingshan Li
DOI:10.1002/chir.23003
日期:2018.9
Cinchonaalkaloid‐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
Asymmetric cooperative catalysis in the conjugate addition of pyrazolones to nitroolefins and subsequent dearomative chlorination
作者:KeFeng Zhang、Feng Li、Jing Nie、JunAn Ma
DOI:10.1007/s11426-013-5017-3
日期:2014.2
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
作者:Jun-Hua Li、Da-Ming Du
DOI:10.1039/c3ob41045e
日期:——
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 enantioselectivities (up to 94% ee) for most substrates under very low catalyst loading (0.25 mol%). This catalytic asymmetric reaction provides valuable and easy access to chiral pyrazol-3-ol derivatives, which possess potential pharmaceutical activity.