Synthesis of hydroxylated oligoarene-type phosphines by a repetitive two-step method

Hydroxylated oligoarene-type phosphines with various substitution patterns were synthesized. Such phosphines have potential as ligands for transition metal-catalyzed reactions. A successful route, which includes a repetitive Suzuki-Miyaura coupling-triflation sequence, reduction, and salt formation, was established starting from 2-bromophenyldicyclohexylphosphine oxide. Other key aspects of the method are the use of suitable triflation reagents and the formation of phosphines as HBF4 salts. Interesting information was obtained from careful analysis of the byproducts in the triflation and reduction steps, and the mechanisms for their formation were proposed.