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Quaternary Phosphonium Compounds


Quaternary phosphonium compounds (QPC), a key class of organophosphorus compounds, can be synthesized by routes involving nucleophilic phosphorus. The synthesis process of QPC shows below.

Synthesis of quaternary phosphonium saltFig 1. Synthesis of quaternary phosphonium salt

Application of Quaternary Phosphonium Compounds in Chemical Reaction

Because of its unique chemical structure, quaternary phosphates are often used as reagents in multiple chemical reactions, such as in Witting reaction, reduction reaction and others. The main chemical reactions are introduced below:

  • Wittig reaction

The Wittig reaction allows the preparation of an alkene by the reaction of an aldehyde or ketone with the ylide generated from a phosphonium salt. The geometry of the resulting alkene depends on the reactivity of the ylide.

Application of QPC in Witting reactionFig 2. Application of QPC in Witting reaction

If R is the primary alkyl methyl or an unimpeded alkyl, the reaction efficiency is higher, while if R is the secondary or higher alkyl, the reaction effect is very poor, and if R is tertiary alkane the salt can't be produced.

  • Reduction reaction

Quaternary phosphonium salt is stable with mild reductant, but it can be reduced by strong reducing agents like sodium, lithium aluminum hydride. The reaction equation shows below.

Reduction reaction of quaternary phosphonium saltFig 3. Reduction reaction of quaternary phosphonium salt

  • Other reaction

A readily available quaternary phosphonium salt containing a trifluoroacetonyl group and a tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BArF4-) counterion was demonstrated to be a highly active Bronsted acid catalyst for Friedel-Crafts-type reactions of an array of electron-rich heteroarenes and aniline derivatives with isatin-derived ketimines, even at 0.1mol% catalyst loadings.

Alfa Chemistry offers various of quaternary phosphonium compounds. You can search the CAS No. or chemical name on our website. If you cannot find them, please feel free to contact us for custom synthesis.