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.
在过去十年中,许多双功能胺-
硫脲被开发为活性
金属-free 有机催化剂。这些
氨基-
硫脲的协同催化作用使得反应速度快并且立体
化学信息的转移优秀。尽管取得了这些令人印象深刻的进展,设计用于不对称催化反应的新型高性能催化剂仍然是有机
化学中的持续关注点。在此,我们描述了一个协同催化系统,由手性
氨基
硫脲和非手性有机酸组成,促进了4-非取代
吡唑酮与亚硝基烯烃的共轭加成及后续的去芳香
氯化反应。在温和的反应条件下,获得了对应的加成产物及后续产物,产率高到优秀(最高可达99%),立体选择性高(最高可达99/1的立体异构体比,98%的对映体过量)。这些转化提供了获得对映体富集的
吡唑衍
生物的便捷途径,这些衍
生物可能具有潜在的药物活性。