Efficient and practical synthesis of 4(5)-aryl-1H-imidazoles and 2,4(5)-diaryl-1H-imidazoles via highly selective palladium-catalyzed arylation reactions.
4(5)-aryl-1H-imidazoles can be efficiently and selectively prepared by PdCl2(dppf)-catalyzed Suzuki-Miyaura reaction of commercially available 4(5)-bromo-1H-imidazole with arylboronic acids under phase-transfer conditions. On the other hand, N-unprotected 4(5)-aryl-1H-imidazoles can undergo highly selective Pd(OAc)2-catalyzed and CuI-mediated direct C-2-arylation with a variety of aryl bromides and iodides under base-free and ligandless conditions to produce 2,4(5)-diaryl-1H-imidazoles in modest to good yields. No N-arylation byproducts are observed under the experimental conditions used to prepare 2,4(5)-diaryl-1H-imidazoles.
Bellina
Fabio
F
Dipartimento di Chimica e Chimica Industriale, University of Pisa, via Risorgimento 35, I-56126 Pisa, Italy. bellina@dcci.unipi.it
Cauteruccio
Silvia
S
Rossi
Renzo
R
D002384:Catalysis; D007093:Imidazoles / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D010165:Palladium / Q000737:chemistry*
D007093:Imidazoles; D010165:Palladium