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Thiosulfinate

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General structure of a thiosulfinate, drawn inexpanded octetstyle[1]

Inorganosulfur chemistry,thiosulfinateis afunctional groupconsisting of the linkage R-S(O)-S-R (R are organic substituents). Thiolsulfinates are also named as alkanethiosulfinic (or arenethiosulfinic) acid esters.

They are the first of the series of functional groups containing an oxidizeddisulfidebond. Other members of this family includethiosulfonates(R-SO2-S-R), α-disulfoxides (R-S(O)-S(O)-R), sulfinyl sulfones (R-S(O)-SO2-R), and α-disulfones (R-SO2-SO2-R), of which all (except α‑disulfoxides[2]) are known. The thiosulfinate group can occur in cyclic as well as acyclic structures.[3][4][5]

Occurrence

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Allicin

A variety of acyclic and cyclic thiosulfinates are found in plants, or formed when the plants are cut or crushed.

A well-known thiosulfinate isallicin,one of the active ingredients formed whengarlicis crushed. Allicin was discovered in 1944 byChester J. Cavallitoand coworkers. Thiosulfinates containing various combinations of themethyl,n-propyl,1-propenyl,2-propenyl,n-butyl,1-butenyl and2-butenylgroups are formed upon crushing differentAlliumas well asBrassicaspecies.[6][7]

Zeylanoxides are cyclic thiosulfinates containing the 1,2-dithiolane-1-oxide ring, isolated from the tropical weedSphenoclea zeylanica.These heterocyclic thiosulfinates arechiralat carbon as well as at sulfur.[8]

Crushing the roots ofPetiveria alliaceaaffords the thiosulfinatesS-(2-hydroxyethyl) 2-hydroxyethane)thiosulfinate,S-(2-hydroxylethyl) phenylmethanethiosulfinate,S-benzyl 2-hydroxyethane)thiosulfinate andS-benzyl phenylmethanethiosulfinate (petivericin; PhCH2S(O)SCH2Ph).[9]Asparagusic acidS-oxide[10]and brugierol[11]are other natural 1,2-dithiolane-1-oxides occurring inAsparagus officinalisandBruguiera conjugata,respectively.

Properties

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Allicin,S-benzyl phenylmethanethiosulfinate, and related thiosulfinates show radical-trappingantioxidantactivity associated with easy formation of sulfenic acids[12]The acyclic thiosulfinates fromAlliumandBrassicaspecies possess antimicrobial, antiparasitic, antitumor and cysteine protease inhibitory activity while the natural 1,2-dithiolane-1-oxides are growth inhibitors. The thiosulfinates fromPetiveriaalso exhibit antimicrobial activity.[13]

Thiosulfinates feature a S(IV) center linked to a S(II) center, the former beingstereogenic.Conversion of simple disulfides to thiosulfinates results in a considerable weakening of the S–S bond from about 70 to 34.5 kcal mol−1(16.7 to 8.25 kJ mol−1) for the S-S bond in PhS(O)SPh,[14]with the consequence that most thiosulfinates are both unstable and quite reactive. For this reason the mixtures of thiosulfinates fromAlliumplants can best be separated byHPLCat room temperature rather than bygas chromatography(GC), although GC has been used with some low molecular weight thiosulfinates. Thiosulfinates can be distinguished fromsulfoxidesbyinfrared spectroscopysince they have a characteristic S=O band at about 1078 cm−1compared to 1030–1060 cm−1in sulfoxides.[15]

Formation and reactions

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Synthetic thiosulfinates were first reported in 1947 by Cavallito and coworkers byoxidationof the corresponding disulfides.[16]

One example of a moderately stable thiosulfinate is thetert-butylderivative, (CH3)3CS(O)SC(CH3)3.This thiosulfinate can be obtained in optical purity by catalyticasymmetric oxidationof di-tert-butyl disulfide withhydrogen peroxide.[17]Upon heating, (CH3)3CS(O)SC(CH3)3decomposes intotert-butanethiosulfoxylic acid (CH3)3CSSOH) as shown by trapping studies.[18]

In a similar manner racemic methyl methanethiosulfinate (CH3S(O)SCH3) can be obtained byperacetic acidoxidation ofdimethyl disulfide.[19]Methyl methanethiosulfinate decomposes thermally giving methanesulfenic acid (CH3SOH), the simplestsulfenic acid,as well asthioformaldehyde(CH2=S). Methyl methanethiosulfinate can also disproportionate to a 1:1 mixture of dimethyl disulfide and methyl methanethiosulfonate (CH3SO2SCH3) and rearrange via aPummerer rearrangementto CH3S(O)CH2SSCH3.[20][21]

An unusual three-membered ring thiosulfinate (a dithiirane 1-oxide) has been prepared through rearrangement of a 1,3-dithietane.[22]A related compound, 3-(9-triptycyl)dithiirane-1-oxide, was prepared by the reaction of (9-triptycyl)diazomethane andS8O.TheX-ray structureof the dithiirane-1-oxide reveals a significantly lengthened sulfur-sulfur bond (211.9(3)pm).[23]

Thiosulfinates have also been invoked as intermediates in the oxidation ofthiolstosulfonic acids.

References

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  1. ^Seesulfoxidefor discussion and references regarding the bonding in divalent monooxosulfur structures.
  2. ^Block, S. S.; Weidner, J. P. (1966) [1 Sept 1964]. "Vibrational behavior and structure of disulfide dioxides (thiolsulfonates)".Applied Spectroscopy.20(2).doi:10.1366/000370266774386272.
  3. ^Kice JL (1980). "Mechanisms and reactivity in reactions of organic oxyacids of sulfur and their anhydrides".Advances in Physical Organic Chemistry.17:65–181.doi:10.1016/S0065-3160(08)60128-8.ISBN9780120335176.
  4. ^Takata, T; Endo, T (1990). "Thiosulphinic acids and esters".The Chemistry of Sulphinic Acids, Esters and Their Derivatives, S. Patai, Ed.(John Wiley, NY): 527–575.doi:10.1002/9780470772270.ch18.ISBN9780470772270.
  5. ^Braverman, S; Cherkinsky, M.; Levinger, S. (2007). "Alkanethiosulfinic Acid Esters".Sci. Synth.39:229–235.
  6. ^Kubec, R; Cody, RB; Dane, AJ; Musah, RA; Schraml, J; Vattekkatte, A; Block, E (2010). "Applications of DART Mass Spectrometry inAlliumChemistry. (Z)-ButanethialS-Oxide and 1-Butenyl Thiosulfinates and theirS-(E)-1-ButenylcysteineS-Oxide Precursor fromAllium siculum".J. Agric. Food Chem.58(2): 1121–1128.doi:10.1021/jf903733e.PMID20047275.
  7. ^Block, E; Dane, AJ; Thomas, S; Cody, RB (2010). "Applications of Direct Analysis in Real Time–Mass Spectrometry (DART-MS) inAlliumChemistry. 2-Propenesulfenic and 2-Propenesulfinic Acids, Diallyl TrisulfaneS-Oxide and Other Reactive Sulfur Compounds from Crushed Garlic and Other Alliums ".J. Agric. Food Chem.58(8): 4617–4625.doi:10.1021/jf1000106.PMID20225897.
  8. ^Hirai, N; Sakashita, S; Sano, T; Inoue, T; Ohigashi, H; Premasthira, C; Asakawa, Y; Harada, J; Fujii, Y (2000). "Allelochemicals of the tropical weedSphenoclea zeylanica".Phytochemistry.55(2): 131–140.doi:10.1016/S0031-9422(00)00264-8.PMID11065289.
  9. ^Kubec, R; Kim, S; Musah, RA (2002)."S-Substituted cysteine derivatives and thiosulfinate formation in Petiveria alliacea--Part II"(PDF).Phytochemistry.61(6): 675–680.doi:10.1016/S0031-9422(02)00328-X.PMID12423888.
  10. ^Yanagawa, H; Kato, T; Kitahara, Y (1973). "Asparagusic acid-S-oxides, new plant growth regulators in etiolated young asparagus shoots ".Tetrahedron Letters.14(13): 1073–1075.doi:10.1016/S0040-4039(01)95907-6.
  11. ^Kato, A; Numata M (1972). "Brugierol and isobrugierol,trans- andcis-1,2-dithiolane-1-oxide, fromBrugiera conjugata".Tetrahedron Letters.13(3): 203–206.doi:10.1016/S0040-4039(01)84280-5.
  12. ^Lynett, PT; Butts, K; Vaidya, V; Garretta, GE; Pratt, DA (2011). "The mechanism of radical-trapping antioxidant activity of plant-derived thiosulfinates".Org. Biomol. Chem.9(9): 3320–3330.doi:10.1039/c1ob05192j.PMID21445384.
  13. ^Kim, S; Kubec, R; Musah, RA (2006)."Antibacterial and antifungal activity of sulfur-containing compounds from Petiveria alliacea"(PDF).Journal of Ethnopharmacology.104(1–2): 188–192.doi:10.1016/j.jep.2005.08.072.PMID16229980.
  14. ^Koch, P; Ciuffarin, E; Fava, A (1970). "Thermal disproportionation of aryl arenethiolsulfinates. Kinetics and mechanism".J. Am. Chem. Soc.92(20): 5971–5977.doi:10.1021/ja00723a026.
  15. ^Block E (2010).Garlic and Other Alliums: The Lore and the Science.Royal Society of Chemistry.ISBN978-0-85404-190-9.
  16. ^Small, LD; Bailey, JH; Cavallito, CJ (1947). "Alkyl thiolsulfinates".J. Am. Chem. Soc.69(7): 1710–1713.doi:10.1021/ja01199a040.PMID20251406.
  17. ^Weix, DJ; Ellman, JA (2005). "(RS)-(+)-2-Methyl-2-Propanesulfinamide [tert-Butanesulfinamide] ".Organic Syntheses.82:157.doi:10.1002/0471264229.os082.24.
  18. ^Block, E (1972). "The Chemistry of Alkyl Thiosulfinate Esters. III. tert-Butanethiosulfoxylic Acid".J. Am. Chem. Soc.94(2): 644–645.doi:10.1021/ja00757a060.
  19. ^Moore, TL; O'Connor, DE (1966). "The Reaction of Methanesulfenyl Chloride with Alkoxides and Alcohols. Preparation of Aliphatic Sulfenate and Sulfinate Esters".J. Org. Chem.31(11): 3587–3592.doi:10.1021/jo01349a027.
  20. ^Block, E; O'Connor, J (1974). "The Chemistry of Alkyl Thiosulfinate Esters. VI. Preparation and Spectral Studies".J. Am. Chem. Soc.96(12): 3921–3929.doi:10.1021/ja00819a033.
  21. ^Block, E; O'Connor, J (1974). "The Chemistry of Alkyl Thiosulfinate Esters. VII. Mechanistic Studies and Synthetic Applications".J. Am. Chem. Soc.96(12): 3929–3944.doi:10.1021/ja00819a034.
  22. ^Ishii, A; Akazawa, T; Ding, MX; Honjo, T; Nakayama, J; Hoshino, M; Shiro, M (1993). "First isolable dithiiranes: 3-(1,1,3,3-tetramethyl-4-oxo-4-phenylbutyl)-3-phenyldithiirane 1-oxides".J. Am. Chem. Soc.115(11): 4914–4915.doi:10.1021/ja00064a072.
  23. ^Ishii, A; Kawai, T; Noji, M; Nakayama, J (2005). "Synthesis and reactions of a monosubstituted dithiirane 1-oxide, 3-(9-triptycyl)dithiirane 1-oxide".Tetrahedron.61(28): 6693–6699.doi:10.1016/j.tet.2005.05.017.
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