Phosphine-phosphonium ylides as ligands in palladium-catalysed C2-H arylation of benzoxazoles

As balanced electron-rich P,C-chelating ligands,phosphine-phosphonium-ylides are considered for their ability to in situ promote palladium-catalysed direct C(sp^2)—H arylation.Using methyl phosphonium salts of 2,2’-bis(diphenylphosphino)-1,1’-binaphtyl("methyl-BINAPIUM")as ylide precursors under optimized reaction conditions,arylation of benzoxazole was found to proceed in moderate to high yield to give functional 2-aryl benzoxazoles.A strong anion effect of the non-salt free ylide was evidenced(TfO^->I^->PF6^-≈salt-free).This first example of phosphonium ylides as ligands in catalytic C-H activation extends the prospect of their general implementation in homogeneous transition metal catalysis.