Phosphorus(V) Sulfide1


[1314-80-3]  · P2S5  · Phosphorus(V) Sulfide  · (MW 222.29) (P4S10)

[15857-57-5]  · P4S10  · Phosphorus(V) Sulfide  · (MW 444.58)

(thiating agent for many different types of compounds;1,2 can activate carboxylic acids and alcohols;3 deoxygenating agent;4 dehydrating agent;5 can undergo electrophilic aromatic substitution at phosphorus6)

Alternate Name: phosphorus pentasulfide.

Physical Data: mp 286-290 °C; bp 514 °C; d 2.09 g cm-3.

Solubility: sol CS2 (0.2 g/100 g) and aq soln of alkali hydroxides; modestly sol ethers, aromatics, tertiary amines, chlorinated solvents, MeCN; reacts with DMSO, primary and secondary amines, alcohols, and neutral or acidic H2O.

Form Supplied in: exists as P4S10; light yellow crystalline solid; widely available.

Analysis of Reagent Purity: melting point, IR.7

Handling, Storage, and Precautions: a highly flammable solid which decomposes in the presence of moisture (including moist air) to form the toxic gas H2S and H3PO4. It is harmful if inhaled or absorbed through the skin. This reagent should be handled with care in a fume hood in the absence of moisture and oxygen.

Use as a Thiating Agent.

Phosphorus pentasulfide accompanied by a base such as pyridine8 or NaHCO3 (Scheeren's reagent)9 has been extensively used as a thiating agent for the conversion of amides,2,10 ketones,11 aldehydes,12 esters,13 S-substituted thioesters,14 phosphinates,15 and acid chlorides16 to thioamides, thiones, thioaldehydes, thioesters, dithioesters, phosphothionates, and thioketenes, respectively. Due to milder reaction conditions, higher yields, and ease of handling, Lawesson's reagent (2,4-Bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-Disulfide) is usually the preferred reagent for these conversions.13,17 Nevertheless, P2S5 accompanied by other agents such as Na2CO3/CF3SO3Me,10 ultrasound,18 alkyllithiums,19 or Et3N20 have been reported to be just as effective and in some cases more cost efficient than Lawesson's reagent. When used in excess, P2S5 has also been shown to convert esters to dithioesters in high yield (eq 1).20b Since the substitution of oxygen by sulfur has been reported to be sensitive to steric effects, the least hindered carbonyl compound will react first when given a choice (eq 2).21

The presence of other functional groups during these conversions can lead to tandem reactions. The reaction of this reagent with 1,4-dicarbonyl compounds results in the formation of thiophenes (eq 3)22 or mesoionic thieno[3,4-f]benzo[c]thiophenes (eq 4).23 On the other hand, 1,3-dicarbonyl compounds give way to different sets of heterocycles depending on the solvent and temperature (eqs 5, 6).24,25 The presence of a nucleophilic amine elsewhere in the molecule can lead to further reactions as well (eqs 7, 8).26,27

Some advantage has also been taken of the enhanced nucleophilic character of thiocarbonyl compounds. Strategically placed leaving groups can thus lead to sulfur-containing heterocycles from thioaldehydes (eq 9),12 thioamides (eqs 10, 11),28,29 and vinylogous thiocarboxylic acids (eq 12).30

In some cases, the conversion of a carbonyl to a thiocarbonyl promotes other reactions as well. When acyclic enones are converted to a,b-unsaturated thiones, for example, a [4 + 2] cycloaddition has been observed (eq 13).31

The conversion of a furan to a thiophene under the aegis of P2S5 has also been reported.5

Activation of Acids and Alcohols.

Similar to other pentavalent phosphorus compounds, P2S5 activates the free hydroxyls of carboxylic acids or alcohols to become good leaving groups. When this activation is done in the presence of another nucleophile, substitution reactions can occur (eq 14).31 Although P2S5/Cl2 has been used to substitute primary alcohols with chlorides,3 other reagents appear to be superior for such transformations.

Use as a Deoxygenating Agent.

P2S5 is one of the most mild and selective reagents for the conversion of sulfoxides to sulfides.4 This reduction will take place selectively without affecting functional groups such as esters, amides (eq 15),32 or ketones.33 Interestingly, sulfones are also unreactive under these conditions.34 Moreover, this reagent can be used for the reduction of sulfilimines to sulfides (eq 16),35 sulfonic acids to polysulfides,36 and sulfines to thiones.37

Use as a Dehydrating Agent.

Surprisingly little use of P2S5 as a dehydrating agent has been reported. The aromatization of furan Diels-Alder adducts (eq 17)5 using P2S5 in CS2 has been reported to be far superior than either HCl/HOAc38 or polyphosphoric acid.5

Use in Electrophilic Aromatic Substitution Reactions.

The formation of Lawesson's reagent from P2S5 and anisole (eq 18)39 is an example of an electrophilic aromatic substitution reaction with this reagent. The addition of Aluminum Chloride facilitates the ability of P2S5 to undergo electrophilic aromatic substitution reactions (eq 19).6

1. Hoffman, H.; Freudenberg, C; Becke-Goehring, M. Top. Phosphorus Chem. 1976, 8, 235.
2. Hurd, R. N.; DeLaMater, G. CRV 1961, 61, 45.
3. Zur, Z.; Dykman, E. CI(L) 1975, 436.
4. Madesclaire, M. T 1988, 44, 6537.
5. Cava, M. P.; VanMeter, J. P. JOC 1969, 34, 538.
6. Olah, G. A.; Berrier, A.; Ohannesian, L. NJC 1986, 10, 253.
7. Gardner, M. JCS(D) 1973, 691.
8. Campaigne, E. CRV 1946, 1, 39.
9. Scheeren, J. W.; Ooms, P. H. J.; Nivard, R. J. F. S 1973, 3, 149.
10. Brillon, D. SC 1990, 20, 3085.
11. Machiguchi, T.; Hasegawa, T.; Kano, Y. BCJ 1993, 66, 3699.
12. Crayston, J.; Iraqi, A.; Mallon, P.; Walton, J. C. JCS(P2) 1993, 9, 1589.
13. Scheibye, S.; Kristensen, J.; Lawesson, S.-O. T 1979, 35, 1339.
14. Trebaul, C. BSF 1971, 1102.
15. Szafraiec, L. J.; Aaron, H. S. JACS 1970, 92, 6391.
16. Schaumann, E. CB 1982, 115, 2755.
17. (a) Pedersen, B. S.; Scheibye, S.; Nilsson, N. H.; Lawesson, S.-O. BSB 1978, 87, 223. (b) Scheibye, S.; Pedersen, B. S.; Lawesson, S.-O. BSB 1978, 87, 229. (c) El-Barbary, A. A.; Clausen, K.; Lawesson, S.-O. T 1979, 36, 3309.
18. Raucher, S.; Klein, P. JOC 1981, 46, 3558.
19. Goel, O. P.; Krolls, U. S 1987, 162.
20. (a) Rao, C. S.; Dave, M. P.; Mody, P. N.; Pandya, A. D. IJC(B) 1976, 14B, 999. (b) Dash, B.; Dora, E. K.; Panda, C. S. H 1982, 19, 2093.
21. Barton, D. H. R.; Choi, L. S. L.; Hesse, R. H.; Pechet, M. M.; Wilshire, C. JCS(P1) 1979, 1166.
22. Musmanni, S.; Ferraris, J. P. CC 1993, 172.
23. Potts, K. T.; McKeough, D. JACS 1973, 95, 2750.
24. Legrand, L. BSF 1959, 1599.
25. Buggle, K.; Ghogain, U. N.; Nangle, M.; MacManus, P. JCS(P1) 1983, 1427.
26. Shinde, B. R.; Shenoy, S. J.; Pai, N. R. IJC(B) 1990, 29B, 711.
27. Molina, P.; Arques, A.; Alias, M. A.; Llamas Saiz, A. L.; Foces-Foces, M. C. LA 1989, 1055.
28. Tanida, H.; Muneyuki, R.; Tsushima, T. BCJ 1975, 48, 3429.
29. Ibrahim, Y. A.; Badawy, M. A.; El-Bahaie, S. JHC 1982, 19, 699.
30. Robins, M. J.; Currie, B. L.; Robins, R. K.; Broom, A. D. CJC 1971, 49, 3067.
31. Blade-Font, A.; Aquila, S.; De Mas, T.; Torres, J. M. JCR(S) 1981, 58.
32. Micetich, R. G. TL 1976, 971.
33. Still, I. W. J.; Hasan, S. K.; Turnbull, K. CJC 1978, 56, 1423.
34. Still, I. W. J.; Hasan, S. K.; Turnbull, K. S 1977, 468.
35. Still, I. W. J.; Turnbull, K. S 1978, 540.
36. Oae, S.; Togo, H. TL 1982, 23, 4701.
37. Kuipers, J. A. M.; Lammerink, B. H. M.; Still, I. W. J.; Zwanenburg, B. S 1981, 295.
38. Cava, M. P.; Scheel, F. M. JOC 1967, 32, 1304.
39. Thomsen, I.; Clausen, K.; Scheibye, S.; Lawesson, S.-O. OS 1984, 64, 158.

Scott D. Edmondson

The Ohio State University, Columbus, OH, USA

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