(Methoxymethyl)triphenylphosphonium bromide is a phosphonium salt used in organic synthesis to generate the corresponding ylide, (methoxymethylidene)triphenyl-λ⁵-phosphane, via deprotonation. This ylide is employed in Wittig reactions with aldehydes to produce α-methoxyalkenes (1-methoxy-1-alkenes or vinyl methyl ethers), which serve as versatile intermediates. These enol ethers are valuable in the synthesis of complex organic molecules, including pharmaceuticals, natural products, and fine chemicals, due to their utility in further transformations such as hydrolysis to α-methoxy carbonyl compounds or participation in umpolung chemistry. The compound's role in forming carbon-oxygen and carbon-carbon bonds highlights its importance as a specialty reagent in advanced synthetic methodologies.