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Sulfenyl chloride

In organosulfur chemistry, a sulfenyl chloride is a functional group with the connectivity R−S−Cl, where R is alkyl[1] or aryl. Sulfenyl chlorides are reactive compounds that behave as sources of RS+. They are used in the formation of RS−N and RS−O bonds. According to IUPAC nomenclature they are named as alkyl thiohypochlorites, i.e. esters of thiohypochlorous acid.

General structural formula of sulfenyl chlorides, RSCl

Typically, sulfenyl halides are stabilized by electronegative substituents. This trend is illustrated by the stability of CCl3SCl obtained by chlorination of carbon disulfide.

Preparation

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Trichloromethane­sulfenyl chloride is a stable sulfenyl chloride

Sulfenyl chlorides are typically prepared by chlorination of disulfides:[2][3]

R2S2 + Cl2 → 2 R−SCl

This reaction is sometimes called the Zincke disulfide reaction, in recognition of Theodor Zincke.[4][5]

Some thioethers (R−S−R’) with electron-withdrawing substituents undergo chlorinolysis of a C−S bond to afford the sulfenyl chloride.[6][7]

In a variation on the Reed reaction, sulfur dichloride displaces hydrogen under UV light.[8]

Reactions

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Perchloromethyl mercaptan (CCl3SCl) reacts with N−H bonds in the presence of base to give the sulfenamides:

CCl3SCl + R2NH → CCl3SNR2 + HCl

This method is used in the production of the fungicides Captan and Folpet.

Sulfenyl chlorides add across alkenes, for example ethylene:[9]

CH2=CH2 + R−SCl → R−SC2H4Cl

They undergo chlorination to the trichlorides:[3]

R−SCl + Cl2 → [R−SCl2]Cl

Sulfenyl chlorides react with water and alcohols to give sulfenyl esters (R−S−O−R′):[10]

R−SCl + H2O → R−SOH + HCl
R−SCl + R'−OH → R−SO−R' + HCl

Route to sulfinyl halides

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Sulfenyl chlorides can be converted to sulfinyl chlorides (RS(O)Cl). In one approach, the sulfinyl chloride is generated in two steps starting with reaction of a thiol (−SH) with sulfuryl chloride (SO2Cl2). In some cases the sulfenyl chloride results instead, as happens with 2,2,2-trifluoro-1,1-diphenylethanethiol. A trifluoroperacetic acid oxidation then provides a general approach to formation of sulfinyl chlorides from sulfenyl chlorides:[11]

 
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Sulfenyl fluorides and bromides are also known.[12] Simple sulfenyl iodides are unstable with respect to the disulfide and iodine, gradually decomposing over the course of several hours at low temperature:

2 R−SI → (R−S)2 + I2

They can be formed metastably from metal mercaptides and iodine, and even form fleetingly when iodine oxidizes neutral thiols to the disulfide. Indeed, sulfenyl iodides are believed to be the active iodinating agents in iodotyrosine biosynthesis.[13] Sulfenyl iodides that are heavily sterically hindered from dimerization are stable.[14]

A related class of compounds are the alkylsulfur trichlorides, as exemplified by methylsulfur trichloride, CH3SCl3.[15]

The corresponding selenenyl halides, R−SeCl, are more commonly encountered in the laboratory. Sulfenyl chlorides are used in the production of agents used in the vulcanization of rubber.

References

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  1. ^ Drabowicz, J.; Kiełbasiński, P.; Łyżwa, P.; Zając, A.; Mikołajczyk, M. (2008). Kambe, N. (ed.). Alkanesulfenyl Halides. Science of Synthesis. Vol. 39. pp. 544–550. ISBN 9781588905307.
  2. ^ Hubacher, Max H. (1943). "o-Nitrophenylsulfur chloride". Organic Syntheses; Collected Volumes, vol. 2, p. 455.
  3. ^ a b Douglass, Irwin B.; Norton, Richard V. (1973). "Methanesulfinyl Chloride". Organic Syntheses; Collected Volumes, vol. 5, pp. 709–715.
  4. ^ Zincke, Th. (1911). "Über eine neue Reihe aromatischer Schwefelverbindungen". Chemische Berichte (in German). 44 (1): 769–771. doi:10.1002/cber.191104401109.
  5. ^ Zincke, Th.; Farr, Fr. (1912). "Über o-Nitrophenylschwefelchlorid und Umwandlungsprodukte". Justus Liebig's Annalen der Chemie (in German). 391 (1): 57–88. doi:10.1002/jlac.19123910106.
  6. ^ F. B. Wells, C. F. H. Allen (1935). "2,4-Dinitroaniline". Organic Syntheses. 15: 22. doi:10.15227/orgsyn.015.0022.
  7. ^ Norman Kharasch, Robert B. Langford (1964). "2,4-Dinitrobenzenesulfenyl Chloride". Organic Syntheses. 44: 47. doi:10.15227/orgsyn.044.0047.
  8. ^ Smith (2020), March's Organic Chemistry, rxn. 14-9.
  9. ^ Brintzinger, Herbert; Langheck, Malte (1954). "Synthesen mit Alkylschwefelchloriden (X. Mitteil. über organische Schwefelchloride)". Chemische Berichte. 87 (3): 325–330. doi:10.1002/cber.19540870306.
  10. ^ Petrovic, Goran; Saicic, Radomir N.; Cekovic, Zivorad (2005). "Phenylsulfenylation of Nonactivated Carbon Atom by Photolysiis of Alkyl Benzenesulfenated: Preparation of 2-Phenylthio-5-heptanol". Organic Syntheses. 81: 244. doi:10.15227/orgsyn.081.0244.
  11. ^ Page, P. C. B.; Wilkes, R. D.; Reynolds, D. (1995). "Alkyl Chalcogenides: Sulfur-based Functional Groups". In Ley, Steven V. (ed.). Synthesis: Carbon with One Heteroatom Attached by a Single Bond. Comprehensive Organic Functional Group Transformations. Elsevier. pp. 113–276. ISBN 9780080423234.
  12. ^ Reno, Daniel S.; Pariza, Richard J. (1998). "Phenyl Vinyl Sulfide". Organic Syntheses; Collected Volumes, vol. 9, p. 662.
  13. ^ Danehy, James P. (1971). "The Sulfur–Iodine Bond". In Senning, Alexander (ed.). Sulfur in Organic and Inorganic Chemistry. Vol. 1. New York: Marcel Dekker. pp. 331–335. ISBN 0-8247-1615-9. LCCN 70-154612.
  14. ^ Sase, S.; Aoki, Y.; Abe, N.; Goto, K. (2009). "Stable Sulfenyl Iodide Bearing a Primary Alkyl Steric Protection Group with a Cavity-shaped Framework". Chemistry Letters. 38 (12): 1188–1189. doi:10.1246/cl.2009.1188.
  15. ^ Braverman, S.; Cherkinsky, M.; Levinger, S. (2008). "Alkylsulfur Trihalides". Sci. Synth. 39: 187–188. ISBN 9781588905307.
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