A practical synthesis of a disulfonated phosphine and its application to biphasic catalysis

Article abstract of DOI:10.1016/S0040-4039(00)00651-1

A convenient synthesis of TPPDS (disodium P-phenyl-3,3'-phosphinediyl- bis(benzenesulfonate)) from triphenylphosphine is described. This represents a quick and reliable way to prepare a water-soluble phosphine with essentially no phosphine oxide formation. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4039(00)00651-1

Tetrahedron Letters 41 (2000) 4503±4505
A practical synthesis of a disulfonated phosphine and its
application to biphasic catalysis
Tim Thorpe,a Stephen M. Brown,b John Crosby,c Steven Fitzjohn,d
James P. Muxworthyb and Jonathan M. J. Williamsa,*
aDepartment of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
bZeneca Agrochemicals, Process Technology Department, Hudders®eld Works, PO Box A38, Leeds Road,
Hudders®eld HD2 1FF, UK
cAstraZeneca, Process R&D, Silk Road Business Park, Charter Way, Maccles®eld, Cheshire SK10 2NA, UK
dZeneca Agrochemicals, Chemical Development Group, Jealott's Hill International Research Station,
Bracknell, Berkshire RG42 6ET, UK
Received 16 March 2000; accepted 20 April 2000
Abstract
A convenient synthesis of TPPDS (disodium P-phenyl-3,30-phosphinediyl-bis(benzenesulfonate)) from
triphenylphosphine is described. This represents a quick and reliable way to prepare a water-soluble
phosphine with essentially no phosphine oxide formation. # 2000 Published by Elsevier Science Ltd.
Complexes of water-soluble phosphines have attracted considerable interest since the development
of the Ruhrchemie/Rhone-Poulenc biphasic hydroformylation process.1 TPPTS [P(m-C6H4SO3Na)3]
was utilised in this process and is the most commonly used phosphine ligand for the preparation of
water-soluble organometallic complexes.2 The preparation of TPPTS is not trivial; this is demon-
strated by the number of communications for its synthesis.3 Often the synthetic procedures are
cumbersome and dicult to reproduce because of the formation of phosphine oxide during the
reaction. Herein, we report on the synthesis of TPPDS [(C6H5)P(m-C6H4SO3Na)2] 1, a water-
soluble phosphine that can be prepared without the formation of phosphine oxide (Scheme 1). The
procedure is straightforward, quick and reliable.
Triphenylphosphine4 (3.0 g, 11.4 mmol) and concentrated sulfuric acid (21 cm3) were placed in
a 500 cm3 round-bottomed ¯ask and stirred at room temperature until dissolution.5 The solution
was then cooled to 0ꢀC before the slow addition of oleum (9.5 cm3, 65 wt% SO3). The ¯ask was
then sealed and the mixture stirred at room temperature for 21 hours. The neutralisation was
carried out at 0ꢀC by the slow, dropwise addition of NaOH (157 cm3, 7.5 M).6 The mixture,
now containing crystalline sodium sulfate was then transferred to a 1000 cm3 round-bottomed ¯ask
* Corresponding author.
0040-4039/00/$ - see front matter # 2000 Published by Elsevier Science Ltd.
PII: S0040-4039(00)00651-1

4504
Scheme 1.
and most of the water removed under vacuum. The remaining solid was re¯uxed in methanol (300
cm3) for 30 min and the solution ®ltered hot to remove the sodium sulfate. The methanol and
residual water were removed under vacuum yielding a white solid. Dissolution of this solid in hot
methanol (300 cm3) followed by the addition of ethyl acetate (850 cm3) caused the precipitation of
.
TPPDS 2H2O on standing. Yield: 3.45 g (60%).
The utility of TPPDS is demonstrated in a biphasic palladium-catalysed Heck reaction.7
TPPTS and TPPMS [(C6H5)2P(m-C6H4SO3Na)] were also used for comparison. Methyl acrylate
2 and iodobenzene 3 were treated with the prepared palladium catalyst in the presence of sodium
acetate (Scheme 2).
Scheme 2.
The results show that each catalyst is e€ective in the formation of methyl cinnamate 4. Leach-
ing levels are also comparable; the percentage leaching represents the amount of palladium
contamination with respect to the amount of palladium catalyst employed.8 TPPDS is readily
accessible by this reported method and performs as well as TPPTS in biphasic palladium-catalysed
Heck reactions.
Acknowledgements
We wish to thank AstraZeneca for the funding for this project.
References
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4505
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5. Protonation of the phosphine provides stability against the oxidising nature of the oleum.
6. The addition of NaOH should take no less than 1 hour due to the exothermic nature of the reaction. It is at this
stage that oxidation of the phosphorus is likely to occur. During the early stages of neutralisation the solution still
has the potential to oxidise and oxidation is more likely at elevated temperatures.
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8. Leaching of palladium was determined as follows: The toluene phase was removed and all volatiles evaporated.
The samples were then extracted with aqua regia (3:1 cHCl:cHNO3, 0.2 cm3). Deionised water (5 cm3) was then
added and the samples centrifuged. Analysis was undertaken on a Perkin±Elmer 1100B atomic absorption
instrument in conjunction with a series of Pd standards.