One pot Pd(OAc)2-catalysed 2,5-diarylation of imidazoles derivatives
作者:Abdelilah Takfaoui、Liqin Zhao、Rachid Touzani、Jean-François Soulé、Pierre H. Dixneuf、Henri Doucet
DOI:10.1016/j.tet.2014.09.012
日期:2014.11
The regioselective 2- or 5-arylation of imidazole derivatives with aryl halides using palladium catalysts has been described in recent years; whereas the arylation at both C2 and C5 carbons of imidazoles in high yields has not been performed. We found conditions allowing the access to these 2,5-diarylimidazoles via a one pot reaction. The choice of the base was found to be crucial to obtain these products in high yields. Using CsOAc as the base, DMA as the solvent and only 2 mol % of the phosphine-free Pd(OAc)(2) the catalyst, the target 2,5-diarylated imidazoles were obtained in moderate to good yields with a wide variety of aryl bromides. Substituents such as fluoro, trifluoromethyl, formyl, acetyl, propionyl, ester, nitro or nitrile on the aryl bromide were tolerated. Sterically congested aryl bromides or heteroaryl bromides can also be employed. Surprisingly the nature of the substituent at position 1 on the imidazole derivative exhibits a huge influence on the reaction. (C) 2014 Elsevier Ltd. All rights reserved.
Highly selective synthesis of 4(5)-aryl-, 2,4(5)-diaryl-, and 4,5-diaryl-1H-imidazoles via Pd-catalyzed direct C-5 arylation of 1-benzyl-1H-imidazole
作者:Fabio Bellina、Silvia Cauteruccio、Annarita Di Fiore、Chiara Marchetti、Renzo Rossi
DOI:10.1016/j.tet.2008.01.051
日期:2008.6
direct C-2 arylation of imidazoles 9 with aryl halides underbase-free and ligandlessconditions. On the other hand, the four-step synthesis of imidazoles 1 from 8 also involves the regioselective bromination of compounds 9 and a Suzuki reaction of the resulting 5-aryl-1-benzyl-4-bromo-1H-imidazoles 11 with arylboronic acids 5 under phase-transfer conditions, followed by N-debenzylation.