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Scott NWJ, Ford MJ, Jeddi N, Eyles A, Simon L, Whitwood AC, Tanner T, Willans CE, Fairlamb IJS. A Dichotomy in Cross-Coupling Site Selectivity in a Dihalogenated Heteroarene: Influence of Mononuclear Pd, Pd Clusters, and Pd Nanoparticles-the Case for Exploiting Pd Catalyst Speciation. J Am Chem Soc 2021; 143:9682-9693. [PMID: 34152135 PMCID: PMC8297865 DOI: 10.1021/jacs.1c05294] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
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Site-selective dihalogenated heteroarene
cross-coupling with organometallic
reagents usually occurs at the halogen proximal to the heteroatom,
enabled by intrinsic relative electrophilicity, particularly in strongly
polarized systems. An archetypical example is the Suzuki–Miyaura
cross-coupling (SMCC) of 2,4-dibromopyridine with organoboron species,
which typically exhibit C2-arylation site-selectivity using mononuclear
Pd (pre)catalysts. Given that Pd speciation, particularly aggregation,
is known to lead to the formation of catalytically competent multinuclear
Pdn species, the influence of these species
on cross-coupling site-selectivity remains largely unknown. Herein,
we disclose that multinuclear Pd species, in the form of Pd3-type clusters and nanoparticles, switch arylation site-selectivity
from C2 to C4, in 2,4-dibromopyridine cross-couplings with both organoboronic
acids (SMCC reactions) and Grignard reagents (Kumada-type reactions).
The Pd/ligand ratio and the presence of suitable stabilizing salts
were found to be critically important in switching the site-selectivity.
More generally, this study provides experimental evidence that aggregated
Pd catalyst species not only are catalytically competent but also
alter reaction outcomes through changes in product selectivity.
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Affiliation(s)
- Neil W J Scott
- Department of Chemistry, University of York, Heslington, York, North Yorkshire YO10 5DD, United Kingdom
| | - Mark J Ford
- Bayer AG, Alfred-Nobel-Strasse 50, 40789 Monheim, Germany
| | - Neda Jeddi
- Department of Chemistry, University of York, Heslington, York, North Yorkshire YO10 5DD, United Kingdom
| | - Anthony Eyles
- Department of Chemistry, University of York, Heslington, York, North Yorkshire YO10 5DD, United Kingdom
| | - Lauriane Simon
- Department of Chemistry, University of York, Heslington, York, North Yorkshire YO10 5DD, United Kingdom
| | - Adrian C Whitwood
- Department of Chemistry, University of York, Heslington, York, North Yorkshire YO10 5DD, United Kingdom
| | - Theo Tanner
- Department of Chemistry, University of York, Heslington, York, North Yorkshire YO10 5DD, United Kingdom
| | - Charlotte E Willans
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
| | - Ian J S Fairlamb
- Department of Chemistry, University of York, Heslington, York, North Yorkshire YO10 5DD, United Kingdom
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