Bromomethyltriphenylphosphonium bromide

The reaction of triphenylphosphine with bromomethyltriphenylphosphonium bromide in refluxing ethanol led, unexpectedly, to methyltriphenylphosphonium bromide in high yield. ... 

Aromatic and aliphatic aldehydes are converted into terminal acetylenes with one extra carbon atom on treatment with bromomethyltriphenylphosphonium bromide and two molar equivalents of potassium t-butoxide. The first reaction step is Wittig olefination the second, dehydrobromination, is sometimes incomplete since the acetylenes are often contaminated with small quantities of 1-bromo-olefins e.g. Scheme 108). 

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