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Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C 6 H 5) 3 and often abbreviated to P Ph 3 or Ph 3 P. It is versatile compound that is widely used as a reagent in organic synthesis and as a ligand for transition metal complexes, including ones that serve as catalysts in organometallic chemistry.
The reaction mechanism of the Mitsunobu reaction is fairly complex. The identity of intermediates and the roles they play has been the subject of debate. Initially, the triphenyl phosphine (2) makes a nucleophilic attack upon diethyl azodicarboxylate (1) producing a betaine intermediate 3, which deprotonates the carboxylic acid (4) to form the ion pair 5.
For example, the reaction of triphenylphosphine with methyl bromide gives methyltriphenylphosphonium bromide: PPh 3 + CH 3 Br → [CH 3 PPh 3] + Br −. The methyl group in such phosphonium salts is mildly acidic, with a pK a estimated to be near 15: [5] [CH 3 PPh 3] + + base → CH 2 =PPh 3 + [Hbase] + This deprotonation reaction gives Wittig ...
The Corey–Fuchs reaction is based on a special case of the Wittig reaction, where two equivalents of triphenylphosphine are used with carbon tetrabromide to produce the triphenylphosphine-dibromomethylene ylide. [2] Step 1 of the Corey-Fuchs reaction, generating the active ylide. This ylide undergoes a Wittig reaction when exposed to an aldehyde.
Building on the reactivity of the triphenylphosphine ligand, the structure of ligands used for the Tsuji–Trost reaction quickly became more complex. Today, these ligands may contain phosphorus, sulfur, nitrogen or some combination of these elements, but most studies have concentrated on the mono- and diphosphine ligands.
[PPh 4]Cl and many analogous compounds can be prepared by the reaction of chlorobenzene with triphenylphosphine catalysed by nickel salts: [5]. PhCl + PPh 3 → [Ph 4 P]Cl. The compound was originally prepared as the corresponding bromide salt (CAS No. 2751-90-8), which in turn was synthesized by passing dry oxygen through the reaction of phenylmagnesium bromide and triphenylphosphine. [6]
The main limitation of the traditional Wittig reaction is that the reaction proceeds mainly via the erythro betaine intermediate, which leads to the Z-alkene. The erythro betaine can be converted to the threo betaine using phenyllithium at low temperature. [18] This modification affords the E-alkene. The Schlosser variant of the Wittig reaction
Akin to complexation, phosphines are readily alkylated. For example, methyl bromide converts triphenylphosphine to the methyltriphenylphosphonium bromide, a "quat salt": PPh 3 + CH 3 Br → [CH 3 PPh 3 +]Br −. Phosphines are nucleophilic catalysts in organic synthesis, e.g. the Rauhut–Currier reaction and Baylis-Hillman reaction.