Pd(OAc) 2-catalyzed cross-coupling of polyfluoroarenes with simple aromatics in imidazolium ionic liquids (ILs) without oxidant and additive and with recycling/reuse of the IL

• Published in: Tetrahedron letters Vol. 52; no. 42; pp. 5525 - 5529
• Main Authors: Kalkhambkar, Rajesh G., Laali, Kenneth K.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 19.10.2011; Elsevier
• Subjects: benzene; chemical reactions; chemical structure; Chemistry; Competitive cross-coupling; Cross-coupling; Exact sciences and technology; Heterocyclic compounds; Heterocyclic compounds with several n hetero atoms in the same ring, in separated rings or in fused rings; ionic liquids; isotopes; Noncondensed benzenic compounds; Organic chemistry; oxidants; Pd(OAc) 2 in imidazolium IL; Polyfluorinated biaryl synthesis; Polyfluoroarenes; Preparations and properties; Primary isotope effect; toluene; Cross-coupling; Polyfluorinated biaryl synthesis; Polyfluoroarenes; Pd(OAc) 2 in imidazolium IL; Primary isotope effect; Competitive cross-coupling; Substituent effect; Organic cation; Mild operating conditions; Nitrogen heterocycle; Oxidant; Ionic liquid; Cross reaction; Aromatic compound; Recycling; Chemical synthesis; Palladium II Acetate; Solvent; Catalytic reaction; Pd(OAc); Carbon-hydrogen bond; Chemical bond; Toluene; Benzene derivatives; Reuse; in imidazolium IL; Chemical coupling; Isotope effect; Fluorine Organic compounds
• ISSN: 0040-4039; 1873-3581
• DOI: 10.1016/j.tetlet.2011.08.077

Polyfluoroarenes can be cross-coupled with simple aromatics (benzene, toluene, and anisole), in good isolated yields, by using Pd(OAc) 2 dissolved in imidazolium ILs [(bmim)PF 6 and (bmim)BF 4] as solvent, without the need for an oxidant and an additive. The reaction is catalyzed by HOAc and it is subject to a primary isotope effect ( K H/ K D = 4.87). Competitive cross-coupling reactions of 1,2,4,5-tetrafluorobenzene with benzene/toluene, benzene/anisole, and anisole/toluene gave K B/ K T = 5.1, K B/ K A = 5.7, and K A/ K T = 5.0, respectively, indicative of a remote substituent effect on Pd insertion into the phenyl C–H bond. Mild reaction conditions, simple product isolation and recycling/reuse of the IL are additional advantages of this method.