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Sonogashira coupling using bulky palladium-phenanthryl imidazolium carbene catalysis
Yudao Ma1, Chun Song, Wei Jiang
1Brigham Young University, Department of Chemistry and Biochemistry, C100 BNSN, Provo, Utah 84602-5700, USA.
Organic Letters
|August 29, 2003
Abstract:
[structure: see text] Bulky phenanthracenyl imidazolium-derived carbene ligands were investigated for copper-free Sonogashira coupling with terminal acetylenes. Aryl bromides and iodides gave coupled products in excellent yields from the Pd(PPh(3))(2)Cl(2) complex with potassium t-butoxide and 18-crown-6 in THF. A remarkable dependence on the size of the ligand was found. The highest yields were obtained with the bulky 2,9-dicyclohexyl-10-phenanthryl ligand 5.