P-Alkynyl functionalized benzazaphospholes as transmetalating agents.
Daniel Y Zhou1, Preston M Miura-Akagi1, Sierra M McCarty1
1Department of Chemistry, University of Hawai'i at Mānoa, 2545 McCarthy Mall, Honolulu, Hawaii 96822, USA. mfcain@hawaii.edu.
Dalton Transactions (Cambridge, England : 2003)
|January 6, 2021
Summary
This study introduces a new alkynyl-functionalized benzazaphosphole for palladium-catalyzed Sonogashira coupling reactions. Fluoride additives were found to circumvent unwanted side reactions, enabling efficient product formation.
Area of Science:
- Organometallic Chemistry
- Catalysis
- Organic Synthesis
Background:
- Benzazaphospholes are versatile heterocyclic compounds with applications in catalysis.
- Palladium-catalyzed cross-coupling reactions are crucial for C-C bond formation.
- Understanding ligand exchange and redox processes is vital for optimizing catalytic cycles.
Purpose of the Study:
- To synthesize and characterize alkynyl-functionalized benzazaphosphole 3.
- To investigate the reactivity of compound 3 in palladium-catalyzed reactions.
- To explore the use of fluoride additives in circumventing side reactions during Sonogashira coupling.
Main Methods:
- Nucleophilic substitution with Grignard reagents.
- Stoichiometric reactions with palladium complexes.
- Cyclic voltammetry and independent electrochemical investigations.
- Sonogashira-type coupling reaction with fluoride additive.
Main Results:
- Alkynyl-functionalized benzazaphosphole 3 was synthesized with an elongated P-C bond.
- Ligand exchange and reductive elimination were observed with palladium complexes.
- Compound 4 exhibited undesired redox processes.
- The addition of tetramethylammonium fluoride (TMAF) enabled efficient Sonogashira coupling.
Conclusions:
- Alkynyl-functionalized benzazaphospholes can participate in palladium-catalyzed cross-coupling reactions.
- Fluoride additives are effective in suppressing side reactions and promoting catalysis.
- This work provides a new strategy for Sonogashira coupling using benzazaphosphole derivatives.
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