Efficient Heck reactions catalyzed by a highly recyclable palladium(II) complex of a pyridyl-functionalized imidazolium-based ionic liquid.
The reactions of 2-(2-pyridyl)imidazole with alkyl iodides at 25 degrees C in the presence of base gave rise to 1-alkyl-2-(2-pyridyl)imidazole. Subsequent neat reactions with alkyl or polyfluoroalkyl halides at 100 degrees C, followed by anion exchange with LiN(SO(2)CF(3))(2), generated the mono-quaternary ionic liquids. All of them have excellent thermal stability and wide liquid range. Most of the salts with asymmetric N-substituents are liquid at room temperature. The effect of N-substituent variation and symmetry on NMR, TGA and DSC is discussed. Reaction of with palladium(II) chloride produced a mononuclear palladium ionic liquid complex, the structure of which was confirmed by single-crystal X-ray diffraction analysis. The Heck cross-coupling reactions using in ionic liquid demonstrated excellent stability and recyclability.
Wang
Ruihu
R
Department of Chemistry, University of Idaho, Moscow, Idaho 83844-2343, USA.
Xiao
Ji-Chang
JC
Twamley
Brendan
B
Shreeve
Jean'ne M
JM
D002384:Catalysis; D018360:Crystallography, X-Ray; D007093:Imidazoles / Q000737:chemistry*; D052578:Ionic Liquids / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010165:Palladium / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D013237:Stereoisomerism
D007093:Imidazoles; D052578:Ionic Liquids; D009942:Organometallic Compounds; D011725:Pyridines; D010165:Palladium