Sequential Pd(II)−Pd(0) Catalysis for the Rapid Synthesis of Coumarins
摘要:
Electrophilic palladium-catalyzed cycloisomerization of brominated aryl propiolates produces brominated coumarins. The brominated cournarins can be diversified by reduction of the Pd(II) catalyst to Pd(O) followed by Suzuki, Sonogashira, Heck, or Hartwig-Buchwald coupling. Thus, a single loading of precatalyst can be used to conduct sequential reactions, allowing the synthesis of functionalized coumarins. Extension of this methodology toward the synthesis of coumarin libraries is discussed.
在此,我们展示了可见光诱导的硒自由基介导的芳基炔酸酯的多米诺骨牌反应,用于合成 1,1-二硒化物烯烃衍生物和含硒 α,β-不饱和羧酸。该工艺温和、不含金属、易于处理且可扩展。脱羧步骤可以通过应用催化量的曙红 Y 染料和碳酸铯作为碱来控制。该方法显示出良好的官能团耐受性,并提供了不错的产品产量。此外,通过制备烯丙醇、α、β-不饱和酯和乙烯基卤化物,进一步扩展了该协议的合成效用。
Photoredox-Catalyzed Cascade Radical Cyclization of Ester Arylpropiolates with CF<sub>3</sub>SO<sub>2</sub>Cl To Construct 3-Trifluoromethyl Coumarin Derivatives
We report a highly efficient method to construct 3-trifluoromethyl coumarins using CF3SO2Cl as the trifluoromethyl radical source with ester 3-arylpropiolates. The reaction incorporated a cascade cyclization/dearomatization/ester migration/oxidization/rearomatization process to afford various 3-trifluoromethyl coumarins under visible light irradiation in good to excellent yields.
我们报告了一种高效的方法来构建3-三氟甲基香豆素,使用CF 3 SO 2 Cl作为带有3-芳基丙酸酯的三氟甲基自由基源。该反应结合了级联环化/脱芳香化/酯迁移/氧化/重芳香化过程,以可见光照射以良好至优异的产率提供了各种3-三氟甲基香豆素。
Synthesis of 1,1-Diarylvinylsulfides via Visible-Light-Promoted Cascade Reaction of Alkynoates with Phenyl Disulfides
Without any additives and photocatalysts, the visible-light-promoted radical cascade reaction between alkynoates and phenyl disulfides has been developed at room temperature. Through S–S bond photolysis and homolytic cleavage, addition of a sulfur radical, aryl migration, decarboxylation, and H atom abstraction, the cascade reaction provides an efficient and practical route to trisubstituted 1,1-diarylvinylsulfides