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  • Title: Three-component synthesis of perfluoroalkyl- or perfluoroaryl-substituted 4-hydroxypyridine derivatives and their palladium-catalyzed coupling reactions.
    Author: Lechel T, Dash J, Hommes P, Lentz D, Reissig HU.
    Journal: J Org Chem; 2010 Feb 05; 75(3):726-32. PubMed ID: 20030386.
    Abstract:
    A three-component reaction with lithiated alkoxyallenes, nitriles, and perfluorinated carboxylic acids as precursors led to a series of perfluoroalkyl- or perfluoroaryl-substituted 4-hydroxypyridine derivatives. These compounds were converted into 4-pyridyl nonaflates which can be employed as versatile building blocks for the synthesis of pi-conjugated compounds with use of palladium-catalyzed couplings. Suzuki reactions at C-4 and C-3 of the pyridine ring proceeded with moderate to high yields. In addition, Suzuki-Miyaura, Stille, or Buchwald-Hartwig coupling reactions have also been studied and afforded the corresponding highly substituted pyridine derivatives. Starting from an arylated propargylic ether the three-component reaction led to a pentasubstituted 4-hydroxypyridine derivative that could also be employed in palladium-catalyzed processes at C-4 and at C-3 of the pyridine core. With this simple approach the sterically highly crowded 3,4,5-triphenyl-substituted pyridine derivative 37a could be prepared and studied by an X-ray analysis. With acetonitrile as precursor a different reaction pathway was found when this component was used in excess resulting in a pyridine derivative with a new substitution pattern. In summary, the methods described here allow a flexible and fairly efficient entry to a variety of highly substituted pyridine derivatives bearing perfluorinated alkyl or aryl groups.
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