Recyclable NHC catalyst for the development of a generalized approach to continuous Buchwald-Hartwig reaction and work-up

Anthony Chartoire, Carmen Claver, Martin Corpet, Jamin Krinsky, Julie Mayen, David Nelson, Steven P. Nolan, Itziar Peñafiel, Robert Woodward, Rebecca E. Meadows

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27 Citations (Scopus)
56 Downloads (Pure)


A generalized approach to the optimization and implementation of Buchwald-Hartwig reactions in flow is reported, through the combination of three key factors: a highly active palladium catalyst; a universal approach for continuous work-up and purification, and a methodology for catalyst recycling and reuse. The palladium N-heterocyclic carbene (NHC) pre-catalyst [Pd(IPr*)(cin)Cl] 4 (IPr* = 1,3-bis(2,6-bis(diphenylmethyl)-4-methylphenyl)imidazol-2-ylidene; cin = η3-cinnamyl) is an excellent choice for continuous Buchwald-Hartwig reactions, due to its inherent high activity and stability. In preparation for running this reaction in flow (published concurrently), a detailed study has been carried out into its water stability, ultimately allowing the recycling of the catalyst in the organic phase up to 3 times in batch mode. A “right-first-time” work-up methodology has also been developed, resulting in a universal protocol that allows the selective extraction of the Buchwald-Hartwig product into the aqueous stream as a salt, while retaining the aryl bromide starting material in the organic stream with the catalyst, thus negating the requirement for further purification. It is therefore envisaged that this approach will particularly amenable to exploitation in the Pharmaceutical industry. An optimized, scalable synthesis of [Pd(IPr*)(cin)Cl] is also reported on multi-hundred gram scale.
Original languageEnglish
Number of pages26
JournalOrganic Process Research and Development
Early online date28 Dec 2015
Publication statusE-pub ahead of print - 28 Dec 2015


  • Buchwald-Hartwig amination
  • NHC catalyst
  • palladium catalysis
  • catalyst recycle
  • continuous processing
  • flow chemistry
  • designed work-up


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