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- Q7127709 subject Q7357983.
- Q7127709 subject Q8343673.
- Q7127709 abstract "Palladium compounds are used as a catalyst in many coupling reactions, usually as a homogeneous catalyst. Examples include: Negishi coupling between an organohalide and an organozinc compound Heck reaction between alkenes and aryl halides Suzuki reaction between aryl halides and boronic acids Stille reaction between organohalides and organotin compounds Hiyama coupling between organohalides and organosilicon compounds Sonogashira coupling between aryl halides and alkynes, with copper(I) iodide as a co-catalyst The Buchwald-Hartwig amination of an aryl halide with an amine The Kumada coupling of grignards and aryl or vinyl halides The Heck-Matsuda Reaction of an arenediazonium salt with an alkeneTypical palladium catalysts used include the following compounds: palladium acetate, Pd(OAc)2 tetrakis(triphenylphosphine)palladium(0), Pd(PPh3)4 bis(triphenylphosphine)palladium(II) dichloride, PdCl2(PPh3)2 [1,1'-bis(diphenylphosphino)ferrocene]palladium(II) dichlorideUnoptimized reactions typically use 10-15 mol% of palladium; where optimized, catalyst loadings can be on the order of 0.1 mol % or below. Palladium nano clusters have been found to catalyze coupling reactions with catalyst loadings as low as parts per billion, however such systems typically do not maintain catalytic activity as long as as well defined ligated catalysts. Many exotic ligands and chiral catalysts have been reported, but they are largely not available commercially, and do not find widespread use. Much work is being done on replacing the phosphine ligands with other classes, such as Arduengo-type carbene complexes, as the phosphine ligands are typically oxygen sensitive (easily oxidized) and must be handled under an inert atmosphere. Phosphines are labile, sometimes requiring additional ligand. For example, Pd(PPh3)4 would be supplemented with PPh3 to keep the palladium coordinated despite loss of the labile phosphine ligands. A concern with the use of palladium in the preparation of pharmaceuticals is that traces of the toxic heavy metal will remain in the product. Column chromatography can be used, but solid-phase metal scavengers (ion exchange resins and derivatives of silica gel) promise more efficient separation.In 2010, the Nobel Prize in Chemistry was awarded to Richard F. Heck, Ei-ichi Negishi and Akira Suzuki for their work on palladium-catalyzed cross couplings in organic synthesis.".
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- Q7127709 comment "Palladium compounds are used as a catalyst in many coupling reactions, usually as a homogeneous catalyst.".
- Q7127709 label "Palladium-catalyzed coupling reactions".
- Q7127709 depiction Sonogashira_coupling_mechanism.png.