Ethylene oxide phosphonium ylide synthesis

Ethylene oxide or 1,2-epoxybutane may also be used for the synthesis of ylides. The resulting ylide is in equilibrium with its conjugated salt (equation 15). The use of ethylene oxide offers some advantages over more conventional bases used in Wittig reactions. The application is simple since ylides and most often also phosphonium salts (from phosphine and alkyl halide) need not to be prepared separately. The reaction medium is neutral, so that base-induced side reactions fail to appear. The method is however less applicable to weakly acid phosphonium salts, since deprotonation requires high temperatures (150 C). 

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