Halide Salts Alleviate TMSOK Inhibition in Suzuki-Miyaura Cross-Couplings
Yao Shi1, Joshua S Derasp1, Sara M Guzman1
1Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.
Suzuki-Miyaura cross-coupling reactions are enhanced by halide additives, which accelerate rates and broaden substrate scope. This study reveals halide salts mitigate catalyst inhibition by potassium trimethylsilanolate (TMSOK) and enable challenging protic heterocycle couplings.
Area of Science:
- Organic Chemistry
- Catalysis
- Reaction Mechanisms
Background:
- Suzuki-Miyaura cross-coupling (SMC) is a vital synthetic tool.
- Recent advances utilize potassium trimethylsilanolate (TMSOK) for rapid reactions.
- TMSOK's inhibitory effects and incompatibility with protic heterocycles limit its application.
Purpose of the Study:
- To conduct a mechanistic investigation of TMSOK-mediated SMC.
- To identify strategies for overcoming TMSOK inhibition.
- To expand the substrate scope of TMSOK-based SMC, including protic heterocycles.
Main Methods:
- Detailed mechanistic study of TMSOK-based SMC conditions.
- Utilized Nuclear Magnetic Resonance (NMR) spectroscopy.
- Investigated the role of halide salt additives.
Main Results:
- Halide salt additives significantly accelerate reaction rates.
- Additives mitigate TMSOK's inhibitory effect by preventing inactive [LnPd(Ar)(μ-OH)]2 formation.
- Active LnPd(Ar)(X) species formation is favored, enabling reactions at low catalyst loadings (0.1 mol %).
- Protic heterocyclic substrates, previously inhibited, are now compatible.
Conclusions:
- Halide additives are crucial for enhancing TMSOK-based SMC.
- Mechanism involves preventing catalyst deactivation and promoting active species.
- Expanded scope includes challenging protic heterocycles, increasing the utility of TMSOK-mediated SMC.
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