Phosphonium salts tetraphenylphosphonium bromide

There are various methods for the synthesis of cyclopropyltriphenylphosphonium bromides, the precursor of choice for the preparation of cyclopropylidenetriphenylphosphoranes. Interestingly, attempts to generate the former salt from cyclopropane derivatives, e.g. 1-bromocy-clopropane, have been unrewarding. One exception is the reaction of cyclopropyllithium with tetraphenylphosphonium bromide followed by elimination of benzene from the initial adduct. The intermediate phosphorane 5 was converted into phosphonium salt 13 by reaction with hydrogen bromide. 

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