Highly Efficient Heck Reactions of Aryl Bromides with n-Butyl Acrylate Mediated by a Palladium/Phosphine-Imidazolium Salt System
Chuluo Yang, Hon Man Lee and Steven P. Nolan*
*Department of Chemistry, University of New Orleans, New
Orleans, Louisiana 70148, Email: steven.nolan
ugent.be
C. Yang, H. Man Lee, S. P. Nolan, Org. Lett., 2001, 3, 1511-1514.
DOI: 10.1021/ol015827s
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Abstract
The combination of Pd(dba)2 and a phosphine-imidazolium salt catalyzes a highly efficient Heck coupling reaction of aryl bromides with n-butyl acrylate in the presence of Cs2CO3 as base.
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Details
The document discusses a study on the highly efficient Heck reactions of aryl bromides with n-butyl acrylate mediated by a palladium/phosphine-imidazolium salt system. Researchers Chuluo Yang, Hon Man Lee, and Steven P. Nolan from the University of New Orleans synthesized a new phosphine-imidazolium salt, L-HBr, and demonstrated its effectiveness in Pd-catalyzed Heck reactions. The catalytic system, consisting of 0.5 mol % Pd(dba)2 and 0.5 mol % L-HBr with 2 equivalents of Cs2CO3 in N,N-dimethylacetamide (DMAc) at 120°C, showed high efficiency, achieving near-complete conversions in less than 3 hours for various aryl bromides. The study highlighted the advantages of using monodentate phosphines and nucleophilic N-heterocyclic carbenes, which provide stability and improved catalytic performance. The system was particularly effective for electron-deficient, electron-neutral, and electron-donating aryl bromides, selectively yielding trans products. However, attempts to use electron-deficient aryl chlorides were unsuccessful. The research suggests that chelating phosphine-carbene ligands are promising for Heck reactions, offering a stable and efficient catalytic system. Further investigations into the scope, limitations, and development of improved ligands, including chiral analogues, are ongoing. The study was supported by the National Science Foundation, the Petroleum Research Fund, and the Albemarle Corporation.
Key Words
ID: J54-Y2001
