Transition Metal‐Free Catalytic C−H Zincation and Alumination

Milan Bisai, Justyna Losiewicz, Lia Sotorrios, Gary Nichol, Andrew Dominey, Michael Cowley, Stephen Thomas, Stuart A. Macgregor, Michael Ingleson

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

C−H metalation is the most efficient method to prepare aryl–zinc and –aluminium complexes that are ubiquitous nucleophiles. Virtually all C–H metalation routes to form Al/Zn organometallics require stoichiometric, strong Brønsted bases with no base-catalyzed reactions reported. Herein we present a catalytic in amine/ammonium salt (Et3N/[(Et3N)H]+) C–H metalation process to form aryl-zinc and aryl-aluminium complexes. Key to this approach is coupling an endergonic C–H metalation step with a sufficiently exergonic dehydrocoupling step between the ammonium salt by-product of C–H metalation ([(Et3N)H]+) and a Zn–H or Al–Me containing complex. This step, forming H2/MeH, makes the overall cycle exergonic while generating more of the reactive metal electrophile. Mechanistic studies supported by DFT calculations revealed metal-specific dehydrocoupling pathways, with the divergent reactivity due to the different metal valency (which impacts the accessibility of amine-free cationic metal complexes) and steric environment. Notably, dehydrocoupling in the zinc system proceeds through a ligand-mediated pathway involving protonation of the -diketiminate Cposition. Given this process is applicable to two disparate metals (Zn and Al), other main group metals and ligand sets are expected to be amenable to this transition metal-free, catalytic C−H metalation.
Original languageEnglish
JournalAngewandte Chemie International Edition
Early online date5 Apr 2024
DOIs
Publication statusE-pub ahead of print - 5 Apr 2024

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