Hydroxylated terphenylphosphine ligands for palladium-catalyzed ortho-selective cross-coupling of dibromophenols, dibromoanilines, and their congeners with Grignard reagents |
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Authors: | Shunpei Ishikawa Kei Manabe |
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Affiliation: | a Manabe Initiative Research Unit, RIKEN Advanced Science Institute, 2-1 Hirosawa, Wako 351-0198, Japan b School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan |
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Abstract: | p-Terphenylphosphines bearing one or two hydroxy groups were used as ligands to palladium in the cross-coupling of dibromophenols, dibromoanilines, and their congeners with Grignard reagents. High ortho-selectivity that cannot be achieved using other phosphine ligands was observed. ortho-Preference was also observed in competitive cross-coupling reactions of two substrates. A significant effect of the concentration of the Grignard reagent on the ortho-selectivity was observed, when the hydroxylated terphenylphosphines were used. Kinetic studies on this effect showed that high concentrations of the Grignard reagent retard the cross-coupling reaction only at the para-position, but not at the ortho-position. |
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Keywords: | Cross-coupling Phosphine Grignard reagent Site-selective Palladium |
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