An Examination of the Palladium/Mor‐DalPhos Catalyst System in the Context of Selective Ammonia Monoarylation at Room Temperature |
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Authors: | Pamela G Alsabeh Dr Rylan J Lundgren Dr Robert McDonald Dr Carin C C Johansson?Seechurn Dr Thomas J Colacot Prof?Dr Mark Stradiotto |
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Institution: | 1. Department of Chemistry, Dalhousie University, 6274 Coburg Road, PO Box 15000, Halifax, Nova Scotia B3H 4R2 (Canada), Fax: (+1)?902‐494‐7190;2. X‐Ray Crystallography Laboratory, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2 (Canada);3. Johnson Matthey Catalysis and Chiral Technologies, Orchard Road, Royston SG8 5HE (UK);4. Johnson Matthey Catalysis and Chiral Technologies, 2001 Nolte Drive, West Deptford, New Jersey 08066 (USA) |
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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 b – f ) 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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Keywords: | amination anilines N P ligands palladium precatalysts |
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