Sulfinyl halide

Methanesulfinyl chloride

Sulfinyl halide groups occur when a sulfinyl functional group is singly bonded to a halogen atom. They have the general formula R-S(O)-X, where X is a halogen, and are intermediate in oxidation level between sulfenyl halides, R-S-X, and sulfonyl halides, R-SO₂-X. The best known examples are sulfinyl chlorides, thermolabile, moisture-sensitive compounds, which are useful intermediates for preparation of other sufinyl derivatives such as sulfinamides, sulfinates, sulfoxides and thiosulfinates.^[1] Unlike the sulfur atom in sulfonyl halides and sulfenyl halides, the sulfur atom in sulfinyl halides is chiral,^[2] as shown for methanesulfinyl chloride.

Sulfinyl chlorides

Sulfinic acid chlorides, or sulfinyl chlorides, are sulfinyl halides with the general formula R-S(O)-Cl. Methanesulfinyl chloride, CH₃S(O)Cl, is prepared by chlorination of dimethyl disulfide in acetic anhydride at -10 to 0 °C.^[3]

These compounds react readily with nucleophiles like water, alcohols, amines, thiols, and Grignard reagents. If the nucleophile is water the product is a sulfinic acid, if it is an alcohol the product is a sulfinic ester, if it is a primary or secondary amine the product is a sulfinamide, if it is a thiol the product is a thiosulfinate, while if it is a Grignard reagent the product is a sulfoxide. Because of their reactivity and instability, alkanesulfinyl chlorides are generally used without purification immediately after their synthesis. Storage is not recommended since pressure develops within the container due to hydrogen chloride release.

Treatment of alkanesulfinyl chlorides having α-hydrogens with tertiary amine bases gives thiocarbonyl S-oxides (sulfines) as isolable compounds. Thus, treatment of n-propanesulfinyl chloride with triethylamine gives syn-propanethial-S-oxide, the lachrymatory agent of the onion.^[4] Treatment of methanesulfinyl chloride or ethane-1,2-bis-sulfinyl chloride, ClS(O)CH₂CH₂S(O)Cl (prepared by oxidative chlorination of 1,2-ethanedithiol, HSCH₂CH₂SH), with a tertiary amine in the presence of the chiral glucose-derived secondary alcohol diacetone-D-glucose affords optically pure sulfinate esters by a process of Dynamic kinetic resolution.^[5][6] Sulfinyl chlorides undergo Friedel–Crafts reactions with arenes giving sulfoxides.

Sulfinyl fluorides, bromides, and iodides

Room temperature hydrolysis of CF₃SF₃ gives the sulfinyl fluoride CF₃S(O)F in a few hours in quantitative yield. Treatment of CF₃S(O)F with hydrogen bromide at -78 °C gives the sulfinyl bromide CF₃S(O)Br, which is unstable at room temperature and readily disproportionates.^[7] Sulfinyl iodides are apparently unknown compounds.

References

1. Braverman, S; Cherkinsky, M.; Levinger, S. (2008). "Alkanesulfinyl Halides". Sci. Synth. 39: 188–196. ISBN 9781588905307.
2. Gilles Hanquet*, Françoise Colobert, Steve Lanners, and Guy Solladié. "Recent developments in chiral non-racemic sulfinyl-group chemistry in asymmetric synthesis" (PDF). Retrieved 13 May 2012.
3. Douglass, I.B.; Norton, R.V. (1973). "Methanesulfinyl chloride". Organic Syntheses. Coll. Vol. 5: 709.
4. Block E., Gillies J.Z., Gillies C.W., Bazzi A.A., Putman D., Revelle L.K., Wang D., Zhang X. (1996). "Allium Chemistry: Microwave Spectroscopic Identification, Mechanism of Formation, Synthesis, and Reactions of (E,Z)-Propanethial S-Oxide, the Lachrymatory Factor of the Onion (Allium cepa)". J. Am. Chem. Soc. 118 (32): 7492–7501. doi:10.1021/ja960722j.
5. Fernández I., Khiar N., Llera J.M., Alcudia F. (1992). "Asymmetric Synthesis of Alkane- and Arenesulfinates of Diacetone-D-glucose (DAG): An Improved and General Route to Both Enantiomerically Pure Sulfoxides". J. Org. Chem. 57 (25): 6789–6796. doi:10.1021/jo00051a022.
6. Khiar N., Araújo C.S., Alcudia F., Fernández I. (2002). "Dynamic Kinetic Transformation of Sulfinyl Chlorides: Synthesis of Enantiomerically Pure C₂-Symmetric Bis-Sulfoxides". J. Org. Chem. 67 (2): 345–356. doi:10.1021/jo0159183.
7. Ratcliffe C.T., Shreeve J.M. (1968). "Some Perfluoroalkylsulfinyl Halides, R_fS(O)X. New Preparations of Trifluoromethylsulfur Trifluoride". J. Am. Chem. Soc. 90: 5403–5408. doi:10.1021/ja01022a013.