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An Examination of the Palladium/Mor-DalPhos Catalyst System in the Context of Selective Ammonia Monoarylation at Room Temperature

Authors

  • Pamela G. Alsabeh,

    1. Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia B3H 4R2 (Canada), Fax: (+1) 902-494-7190
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  • Dr. Rylan J. Lundgren,

    1. Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia B3H 4R2 (Canada), Fax: (+1) 902-494-7190
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  • Dr. Robert McDonald,

    1. X-Ray Crystallography Laboratory, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2 (Canada)
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  • Dr. Carin C. C. Johansson Seechurn,

    1. Johnson Matthey Catalysis and Chiral Technologies, Orchard Road, Royston SG8 5HE (UK)
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  • Dr. Thomas J. Colacot,

    1. Johnson Matthey Catalysis and Chiral Technologies, 2001 Nolte Drive, West Deptford, New Jersey 08066 (USA)
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  • Prof. Dr. Mark Stradiotto

    Corresponding author
    1. Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia B3H 4R2 (Canada), Fax: (+1) 902-494-7190
    • Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia B3H 4R2 (Canada), Fax: (+1) 902-494-7190
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  • Mor-DalPhos=di(1-adamantyl)-2-morpholinophenylphosphine.

Abstract

An examination of the [{Pd(cinnamyl)Cl}2]/Mor-DalPhos (Mor-DalPhos=di(1-adamantyl)-2-morpholinophenylphosphine) catalyst system in Buchwald–Hartwig aminations employing ammonia was conducted to better understand the catalyst formation process and to guide the development of precatalysts for otherwise challenging room-temperature ammonia monoarylations. The combination of [{Pd(cinnamyl)Cl}2] and Mor-DalPhos afforded [(κ2-P,N-Mor-DalPhos)Pd(η1-cinnamyl)Cl] (2), which, in the presence of a base and chlorobenzene, generated [(κ2-P,N-Mor-DalPhos)Pd(Ph)Cl] (1 a). Halide abstraction from 1 a afforded [(κ3-P,N,O-Mor-DalPhos)Pd(Ph)]OTf (5), bringing to light a potential stabilizing interaction that is offered by Mor-DalPhos. An examination of [(κ2-P,N-Mor-DalPhos)Pd(aryl)Cl] (1 bf) and related precatalysts for the coupling of ammonia and chlorobenzene at room temperature established the suitability of 1 a in such challenging applications. The scope of reactivity for the use of 1 a (5 mol %) encompassed a range of (hetero)aryl (pseudo)halides (X=Cl, Br, I, OTs) with diverse substituents (alkyl, aryl, ether, thioether, ketone, amine, fluoro, trifluoromethyl, and nitrile), including chemoselective arylations.

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