Abstract
Nucleophilic N-heterocyclic carbenes (NHC) have been used as ancillary ligands in palladium-mediated Suzuki-Miyaura cross-coupling reactions involving aryl chlorides or aryl triflates with arylboronic acids. The scope of the coupling process using Pd(0) or Pd(II) sources and an imidazolium salt in the presence of a base, Cs2CO3, was tested using various substrates. The Pd(OAc)(2) or Pd-2(dba)(3)/IMes.HCl (2, IMes = 1,3-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene) system presents very high activity with respect to electron-neutral and electron-rich aryl chlorides. The ligand IPr.HCl (3, IPr = 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene) is also effective for the Suzuki-Miyaura cross-coupling involving a wide spectrum of aryl chlorides and aryl triflates. The general protocol developed has been applied successfully to the synthesis of an antiinflammatory drug (Fenbufen) and to a key intermediate in the synthesis of sartans. Mechanistically, palladium-to-ligand ratio studies support an active palladium species bearing one nucleophilic carbene ligand.
Original language | English |
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Pages (from-to) | 2866-2873 |
Number of pages | 8 |
Journal | Organometallics |
Volume | 21 |
Issue number | 14 |
DOIs | |
Publication status | Published - 8 Jul 2002 |
Keywords
- N-HETEROCYCLIC CARBENES
- PALLADIUM-CATALYZED AMINATION
- ASTERISK = ETA(5)-C5ME5
- ARYL CHLORIDES
- NUCLEOPHILIC-CARBENE
- OLEFIN METATHESIS
- ROOM-TEMPERATURE
- ORGANOBORON COMPOUNDS
- GRIGNARD-REAGENTS
- ARYLBORONIC ACIDS