Phosphine ligands 1758 INDEX

As an illustration, consider the oxidation of acyclic phosphines by bis (2-hydroxyethyl) disulfide which proceeds with retention of configuration at phosphorus. The essential portion of this reaction, and appropriate ligand indexing, are shown in Eq. (13) for the oxidation of (/ )-methylphenyl-propylphosphine (29). 

Applications of these C-H activation processes in polymerization reactions have also been reported in the literature. For example, a palladium-catalyzed C-H arylation polycondensation was carried out between a thiophene unsubstituted at the 2- and 5- positions and its 2,5-dibromo derivative. The transformation was effected in the presence of palladium acetate, a phosphine, and cesium carbonate in DMF at 100 °C for 48 h (eq 23). A survey of different phosphines showed that similar yields, molecular weights (Mn), and polydispersity indexes (PDI) could be obtained using di-tert-butyl(methyl)phosphonium tetrafluoroborate or tri-cyclohexylphosphonium tetrafluoroborate as the ligand. ... 

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