Phosphonium salts purification

Loss of metal by ligand degradation. The oxidation of phosphorus ligands by peroxide impurities in the feed is an example. Purification of the feed is an obvious remedy. It is much more difficult to find a solution when ligand degradation is inherent to the catalytic reaction mechanism (e.g., phosphonium salt formation). 

A series of conjugated polyenes capped with chromophores and containing an androstane spacer were synthesized by Wittig or Wittig-type olefinations from epi-androsterone 5150. For example, vinyl carboxaldehyde 52, prepared from 51 in 60% yield as shown in equation 32, was treated with 9-anthrylmethylphosphonium bromide and n-butyllithium to give diene 53. Exocyclic diene 53 was subsequently oxidized to vinyl carboxaldehyde 54. The androsterone vinyl aldehyde intermediate could either be treated with a tetraphenylporphyrinpolyenyl phosphonium ylide, or, as shown below, the phosphonium salt of the androsterone (55) could be reacted with TPP polyeneal 56. The desired all-(E) isomer, 57, was obtained from the ( )/(Z)-isomeric mixture by chromatographic purification. 

The submitter states that the slight excesses of phenyllithium (5 ) and methyltriphenylphosphonium iodide (10%) specified ensure complete corversion of the aldehyde and simplify the purification of the product since the excess phosphonium salt is readily removed during filtration through Florosil. 

A novel methanofullerene (4) containing a stable phosphorus ylide has been obtained from the reaction of C60 with triphenylphosphine and dimethyl acetyle-nedicarboxylate. An improved route to benzyl-, thienyl- and dimethylamino-phenyl-substituted phosphonium salts has been described (scheme 1). The new method has several advantages over previous routes, including high yields and ease of purification. 

Methyl-9,10-dihydro-9-phosphaphenanthrene-9-oxide (3).1 The phosphonium salt 2 (R = Me) (0.7 g, 1.5 mmol) in aqueous acetone containing KOH solution was heated to reflux for 2 h. Extraction of the cold mixture with CHCI3, evaporation of the solvent and chromatography (silica gel, EtOAc EtOH 7 3) afforded 0.24 g of 3 (71%). Purification by preparative TLC with EtOAc. 

Biocides. Quaternary phosphonium salts are known to be biocides and can be useful in various applications based on this attribute(e.g., purification of beer in the brewing industry). The ionomer has an added advantage in that it can be recovered easily and be regenerated for repeated applications. 

Gerritsma, D. A., Robertson, A., McNulty, J. Capretta, A. (2004). Heck reactions of aryl halides in phosphonium salt ionic liquids library screening and applications. Tetrahedron Letters, 45,41, 7629-7631, ISSN 0040-4039 Giiell, R., Antico, E., Salvado, V. Fontas, C. (2008). Efficient hollow fiber supported liquid membrane system for the removal and preconcentration of Cr(VI) at trace levels. Separation and Purification Technology, 62,2,389-393, ISSN 1383-5866 Guibal, E., Vincent, T. Jouannin, C. (2009). Immobilization of extractants in biopolymer capsules for the synthesis of new resins a focus on the encapsulation of tetraalkyl phosphonium ionic liquids. Journal of Materials Chemistry, 19, 45, 8515-8527, ISSN 0959-9428... 

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