Borane Catalyzed Selective Diazo Cross-Coupling Towards Pyrazoles,Advanced Synthesis & Catalysis

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Borane Catalyzed Selective Diazo Cross-Coupling Towards Pyrazoles
Advanced Synthesis & Catalysis ( IF 4.4 ) Pub Date : 2021-11-25 , DOI: 10.1002/adsc.202101312
Ayan Dasgupta ₁ , Sanjukta Pahar ₁ , Rasool Babaahmadi ₂ , Lukas Gierlichs ₁ , Brian Yates ₂ , Alireza Ariafard ₂ , Rebecca Melen ₁

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Decomposition of donor-acceptor diazo compounds leads to the formation of reactive carbene intermediates. These can undergo a wide variety of carbene transfer reactions to yield synthetically useful products. Herein, we report a selective borane catalyzed cyclization reaction from the combination of two different diazo compounds to afford N-substituted pyrazoles. The selective decomposition of the more reactive α-aryl α-diazoester and subsequent reaction with a vinyl diazoacetate produces N-alkylated pyrazoles in a regioselective manner. Catalytic amounts of tris(pentafluorophenyl)borane (10 mol%) were employed to afford the pyrazole products (36 examples) in yields from 59 to 80%. Extensive DFT studies have been undertaken to interpret the mechanism for this reaction which was found to go through two tandem catalytic cycles, both catalyzed by B(C₆F₅)₃.

中文翻译：

硼烷催化的吡唑选择性重氮交叉偶联

供体-受体重氮化合物的分解导致反应性卡宾中间体的形成。这些可以进行多种卡宾转移反应以产生合成有用的产品。在此，我们报道了一种选择性硼烷催化的环化反应，由两种不同的重氮化合物组合得到 N-取代的吡唑。更具反应性的 α-芳基 α-重氮酯的选择性分解和随后与重氮乙酸乙烯酯的反应以区域选择性方式产生 N-烷基化吡唑。使用催化量的三(五氟苯基)硼烷(10 mol％)以59至80％的产率提供吡唑产物(36个实施例)。已经进行了广泛的 DFT 研究来解释该反应的机理，发现该反应经历了两个串联催化循环，均由 B（C₆楼₅ ) ₃．

更新日期：2021-11-25

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