Methyltriphenylphosphonium bromide explained

Methyltriphenylphosphonium bromide is the organophosphorus compound with the formula [(C₆H₅)₃PCH₃]Br. It is the bromide salt of a phosphonium cation. It is a white salt that is soluble in polar organic solvents.

Synthesis and reactions

Methyltriphenylphosphonium bromide is produced by treating triphenylphosphine with methyl bromide:^[1]

Ph₃P + CH₃Br → Ph₃PCH₃Br

Methyltriphenylphosphonium bromide is the principal precursor to methylenetriphenylphosphorane, a useful methylenating reagent. This conversion is achieved by treating methyltriphenylphosphonium bromide with strong base.^[2]

Ph₃PCH₃Br + BuLi → Ph₃PCH₂ + LiBr + BuH

References

1. Georg. Wittig. U.. Schoellkopf . 1960. Methylenecyclohexane. Organic Syntheses. 40. 66. 10.15227/orgsyn.040.0066.
2. 10.1080/00397918508063883. The Wittig Reaction Using Potassium-tert-butoxide High Yield Methylenations of Sterically Hindered Ketones. 1985. Fitjer. Lutz. Quabeck. Ulrike. Synthetic Communications. 15. 10. 855–864.