Thiosulfinate
In organosulfur chemistry, thiosulfinate is a functional group consisting of the linkage R-S(O)-S-R (R are organic substituents). The thiosulfinate functional group is rare, but these compounds are invoked as intermediates in the oxidation of thiols to sulfonic acids, which is a common transformation. They feature a S(IV) center linked to a S(II) center, the former being stereogenic. A well-known thiosulfinate is allicin, one of the active ingredients in garlic, discovered and synthesized in 1944 by Chester J. Cavallito and coworkers.
One example of a moderately stable thiosulfinate is the tert-butyl derivative, (CH3)3CS(O)SC(CH3)3. This thiosulfinate can be obtained in optical purity by catalytic asymmetric oxidation of di-tert-butyl disulfide with hydrogen peroxide.[1] Upon heating, (CH3)3CS(O)SC(CH3)3 decomposes into tert-butanethiosulfoxylic acid (CH3)3CSSOH) as shown by trapping studies.[2]
In a similar manner racemic methyl methanethiosulfinate (CH3S(O)SCH3) can be obtained by peracetic acid oxidation of dimethyl disulfide.[3] Methyl methanethiosulfinate decomposes thermally giving methanesulfenic acid (CH3SOH), the simplest sulfenic acid, as well as thioformaldehyde (CH2S). It can also disproportionate to a 1:1 mixture of dimethyl disulfide and methyl methanethiosulfonate (CH3SO2SCH3) and rearrange via a Pummerer rearrangement to CH3S(O)CH2SSCH3).[4][5]
[edit] References
- ^ Daniel J. Weix and Jonathan A. Ellman "(RS)-(+)-2-Methyl-2-Propanesulfinamide [tert-Butanesulfinamide]" Organic Syntheses, Vol. 82, p.157 (2005).
- ^ Eric Block "The Chemistry of Alkyl Thiosulfinate Esters. III. tert-Butanethiosulfoxylic Acid" J. Am. Chem. Soc., Vol. 94, p. 644-645 (1972).
- ^ T. L. Moore and D. E. O'Connor "The Reaction of Methanesulfenyl Chloride with Alkoxides and Alcohols. Preparation of Aliphatic Sulfenate and Sulfinate Esters" J. Org. Chem., Vol. 31, p. 3587-3592 (1966).
- ^ Eric Block and John O'Connor "The Chemistry of Alkyl Thiosulfinate Esters. VI. Preparation and Spectral Studies" J. Am. Chem. Soc., Vol. 96, p. 3921-3929 (1974).
- ^ Eric Block and John O'Connor "The Chemistry of Alkyl Thiosulfinate Esters. VII. Mechanistic Studies and Synthetic Applications" J. Am. Chem. Soc., Vol. 96, p. 3929-3944 (1974).
