Metal-Free Synthesis of Aryltriphenylphosphonium Bromides by the Reaction of Triphenylphosphine with Aryl Bromides in Refluxing Phenol

A metal-free synthesis of aryltriphenylphosphonium bromides by the reaction of triphenylphosphine with aryl bromides in refluxing phenol is developed. This reaction tolerates hydroxymethyl, hydroxyphenyl, and carboxyl groups in aryl bromides, allowing to synthesize multifunctional aryltriphenylphosphonium bromides, from which facile access to multifunctional aryldiphenylphosphines and their oxides by hydrolysis and subsequent reduction is exemplified. A two-step addition-elimination mechanism, with the elimination step being a fast step, is also proposed.