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Sequential Pd(II)−Pd(0) Catalysis for the Rapid Synthesis of Coumarins

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journal contribution
posted on 05.08.2005, 00:00 by Kelin Li, Yibin Zeng, Ben Neuenswander, Jon A. Tunge
Electrophilic palladium-catalyzed cycloisomerization of brominated aryl propiolates produces brominated coumarins. The brominated coumarins can be diversified by reduction of the Pd(II) catalyst to Pd(0) 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.