Sodium Benzenesulfinate1

(1; R = Ph)

[873-55-2]  · C6H5NaO2S  · Sodium Benzenesulfinate  · (MW 164.17) (1).2H2O

[25932-11-0]  · C6H9NaO4S  · Sodium Benzenesulfinate  · (MW 200.21) (2; R = p-Tol)

[824-79-3]  · C7H7NaO2S  · Sodium p-Toluenesulfinate  · (MW 178.20) (2).2H2O

[7257-26-3]  · C7H11NaO4S  · Sodium Benzenesulfinate  · (MW 214.24)

(formation of saturated and unsaturated sulfones;2 synthesis of thiosulfonates;3 preparation of p-tolylsulfonyldiazomethane4 and p-tolylsulfonylmethyl isocyanide5)

Physical Data: (1) mp >300 °C; (2) mp >300 °C.

Solubility: sol H2O.

Form Supplied in: white solids; widely available.

Analysis of Reagent Purity: (1) 97-98% purity; (2) 97-98% purity containing 9-18% H2O; anhydrous reagent commercially available.

Handling, Storage, and Precautions: both sodium sulfinates can be dried in a vacuum oven at 140 °C overnight to remove the water of hydration.

Preparation of Sulfones.

Sodium benzenesulfinate (1) and sodium p-toluenesulfinate (2) are ambident nucleophiles that react with soft electrophiles, such as alkyl halides, to form sulfones as the major product. Hard electrophiles, such as diazomethane, react to yield predominantly sulfinic esters, although substantial quantities of sulfone may be produced (eq 1).6,7 (Sulfinic esters are best produced by alternate procedures; see Methyl Benzenesulfinate.) The amount of sulfinic ester impurity, typical in the preparation of a sulfone, can be reduced greatly by performing the alkylation under phase-transfer conditions,8 or by preforming the tetrabutylammonium sulfinate salt.9 Numerous reactions of arenesulfinates with simple electrophiles to form sulfones have been reported in the early literature.10

Aryl alkyl sulfones can readily form a-sulfonyl carbanions by treatment with Grignard reagents or alkyllithium reagents;11,12 other bases that have been used include Lithium Diisopropylamide, Lithium Amide and Sodium Amide, Sodium Hydride, and potassium alkoxides.11 Reagent (2) has been used to introduce a sulfone as an activating group for the Michael addition of a benzyl group to acrylonitrile; the sulfonyl group was removed easily by reductive cleavage with Sodium Amalgam (eq 2).13

Reagent (2) can add to a,b-unsaturated ketones in the presence of AcOH to form g-oxo sulfones.14 These intermediates are useful for the b-alkylation of a,b-unsaturated ketones since the sulfonyl group can be eliminated easily with base to reform the double bond (eq 3).

Allylic sulfones are useful synthetic intermediates that can be prepared from either (1) or (2) and a variety of allylic starting materials.15 Allylic nitro compounds undergo denitro-sulfonylation in the presence of (1)/AcOH,16 or in the presence of Tetrakis(triphenylphosphine)palladium(0);17,18 the latter reaction occurs with high regioselectivity to afford the product from direct displacement of the nitro group (eq 4).

Allylic bromides reportedly react with (1) or (2) to form sulfones via a classical SN2 mechanism, but equilibrate to the more thermodynamically stable compound in the presence of catalytic amounts of the same sulfinate.19 A general synthesis of 1,5-dienes via coupling of an allylic halide and an allylic sulfone followed by reductive cleavage of the sulfone has been reported (eq 5).20 In this account, Lithium-Ethylamine was found to be preferred to Na(Hg) for removal of the sulfonyl group, since the use of Na(Hg) resulted in double-bond migration.

Unsaturated sulfones can be prepared via iodosulfonylation of alkenes and conjugated dienes with (1) or (2) in the presence of Iodine.21,22 Alkenes react stereospecifically with (1)/I2 to form 2-iodo sulfones, while 1,3-dienes react to form d-iodo allylic sulfones. The iodo functionality can be substituted by various nucleophiles or undergo dehydrohalogenation to form allylic sulfones or 1-sulfonyl-1,3-dienes, respectively (eq 6).

Alternatively, addition of (1) to a 1,3-diene in the presence of Mercury(II) Chloride results in the formation of 2-(phenylsulfonyl)-1,3-dienes (eq 7).23 These versatile intermediates can participate in Michael-type additions and cycloaddition reactions.24-26

Substituted vinyl sulfones also may be prepared by addition of (1) to alkynyl esters in the presence of Boric Acid (eq 8).27 These vinyl sulfones serve as excellent dienophiles in Diels-Alder reactions, containing useful functionality for further transformation.28 In general, vinyl sulfones serve as valuable synthetic intermediates.29

Catalytic quantities of (1) have also been used in a highly efficient [3 + 2] cyclization-elimination reaction of (phenylsulfonyl)allene in the presence of a,b-unsaturated compounds to produce cyclopentenyl-substituted sulfones; other nucleophiles such as cyanide or nitrite will work as well (eq 9).30

Preparation of Thiosulfonates.

(1) or (2) react with elemental sulfur in various amines or liquid ammonia to produce thiosulfonate salts.3 These salts can be alkylated to form thiosulfonate esters in good yield (eq 10); these compounds are useful sulfenylating agents (eq 11).31

Preparation of p-Tolylsulfonyldiazomethane.

(2) has been used for preparing p-tolylsulfonyldiazomethane,4 a useful reagent for the synthesis of trisubstituted-methane derivatives,32 and the conversion of allylic alcohols to homoallylic alcohols.33 This a-diazo sulfone also reacts with alkenes to provide sulfonyl-substituted cyclopropanes (eq 12).32,34

Preparation of p-Tolylsulfonylmethyl Isocyanide.

(2) also has been utilized for the preparation of p-Tolylsulfonylmethyl Isocyanide (TosMIC),5 a useful reagent for the formation of various azole ring systems.35 Base-induced addition of the C-N=C moiety into the C=O functionality of an aldehyde, for example, produces oxazoles in excellent yield (eq 13).36 Other ring systems such as imidazoles, thiazoles, pyrroles, and 1,2,4-triazoles can be manufactured via reaction with C=S-, C=C-, C=O-, and N=N-containing substrates, respectively. This reagent also has been utilized for the conversion of ketones into cyanides,37 and the synthesis of a-hydroxy aldehydes.35

1. For a general review of sulfinic acids and sulfinate salts, see: The Chemistry of Sulfinic Acids, Esters, and Their Derivatives; Patai, S., Ed.; Wiley: Chichester, 1990.
2. Schank, K. In The Chemistry of Sulfones and Sulfoxides; Patai, S.; Rappoport, Z.; Stirling, C., Eds.; Wiley: Chichester, 1988; pp 165-232.
3. Sato, R.; Goto, T.; Takikawa, Y.; Takizawa, S. S 1980, 615.
4. van Leusen, A. M.; Strating, J. OS 1977, 57, 95.
5. Fieser, M. FF 1988, 13, 313, and referenced preceeding volumes. p-Tolylsulfonylmethyl isocyanide currently is widely available.
6. Meek, J. S.; Fowler, J. S. JOC 1968, 33, 3422.
7. Field, L. S 1972, 101.
8. Crandall, J. K.; Pradat, C. JOC 1985, 50, 1327.
9. Vennstra, G. E.; Zwaneburg, B. S 1975, 519.
10. Suter, C. M. The Organic Chemistry of Sulfur; Wiley: New York, 1944; p. 658.
11. Oae, S.; Uchida, Y. In The Chemistry of Sulfones and Sulfoxides; Patai, S.; Rappoport, Z.; Stirling, C., Eds.; Wiley: Chichester, 1988; pp 583-664.
12. Field, L. S 1978, 713.
13. Sanchez, I. H.; Aguilar, M. A. S 1981, 55.
14. Fayos, J.; Clardy, J.; Dolby, L. J.; Farnham, T. JOC 1977, 42, 1349.
15. Padwa, A.; Murphree, S. S. Rev. Heteroat. Chem. 1992, 6, 241.
16. Barlaam, B; Boivin, J.; Zard, S. Z. TL 1990, 51, 7429.
17. Tamura, R.; Hayashi, K.; Kakihana, M.; Tsuji, M.; Oda, D. TL 1985, 26, 851.
18. Ono, N.; Hamamoto, I.; Yanai, T.; Kaji, A. CC 1985, 523.
19. Colombani, D.; Navarro, C; Degueil-Castaing, M.; Maillard, B. SC 1991, 21, 1481.
20. Grieco, P. A.; Masaki, Y. JOC 1974, 39, 2135.
21. Barluenga, J.; Rodriguez, M. A.; Campos, P. J.; Asensio, G. CC 1987, 1491.
22. Barluenga, J.; Martínez-Gallo, J. M.; Nájera, C.; Fañanás, F. J.; Yus, M. JCS(P1) 1987, 2605.
23. Bäckvall, J.-E.; Juntunen, S. K.; Andell, O. S. OS 1989, 68, 148.
24. Bäckvall, J.-E.; Juntunen, S. K. JOC 1988, 53, 2398.
25. Overman, L. E.; Petty, C. B.; Ban, T.; Huang, G. T. JACS 1983, 105, 6335.
26. Eisch, J. J.; Galle, J. E.; Hallenbeck, L. E. JOC 1982, 47, 1608.
27. Hirst, G. C.; Parsons, P. J. OS 1990, 69, 169.
28. Buss, A. D.; Hirst, G. C.; Parsons, P. J. CC 1987, 1836.
29. Fuchs, P. L.; Braish, T. F. CRV 1986, 86, 903.
30. Padwa, A.; Yeske, P. E. JACS 1988, 110, 1617.
31. (a) Trost, B. M. CRV 1978, 78, 363. (b) Scholz, D. LA 1984, 259. (c) Mitsudera, H. Kamikado, T.; Uneme, H.; Manabe, Y. ABC 1990, 54, 1723.
32. van Leusen, A. M.; Strating, J. Quart. Rep. Sulfur Chem. 1970, 5, 67.
33. Bruckner, R.; Peiseler, B. TL 1988, 29, 5233.
34. Padwa, A.; Wannamaker, M. W.; Dyszlewski, A. D. JOC 1987, 52, 4760.
35. Hoogenboom, B. E.; Oldenziel, O. H.; van Leusen, A. M. OS 1977, 57, 102 and references cited therein.
36. van Leusen, A. M.; Hoogenboom, B. E.; Siderius, H. TL 1972, 23, 2369.
37. Becker, D. P.; Flynn, D. L. S 1992, 1080.

Jeffrey D. Macke

Miles, Kansas City, MO, USA

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