Sulfonium

Source: Wikipedia, the free encyclopedia.
Structure of (CH3)3S+. The C-S-C angles are 102° and C-S bond distance is 177 picometers.[1]

In

organic solvent.[2][3]

Synthesis

Sulfonium compounds are usually

trimethylsulfonium iodide
:

CH
3–S–CH
3 + CH
3–I → (CH
3)
3S+
I−

The reaction proceeds by a nucleophilic substitution mechanism (SN2). Iodide is the leaving group departs. The rate of methylation is faster with more electrophilic methylating agents, such as methyl trifluoromethanesulfonate.

seaweeds.[4]

Inversion

Sulfonium ions with three different substituents are chiral owing to their pyramidal structure. Unlike the isoelectronic oxonium ions (R3O+), chiral sulfonium ions are resolvable into optically stable enantiomers.[5] [Me(Et)SCH2CO2H]+ is the first chiral sulfonium cation to be resolved into enantiomers.[6] The barrier to inversion ranges from 100 to 130 kJ/mol.[3]

Applications and occurrence

Biochemistry

The sulfonium (more specifically

S-adenosylmethionine occurs widely in nature, where it is used as a source of the adenosoyl or methyl radicals. These radicals participate in the biosynthesis of many compounds.[7][8]

S-adenosylmethionine
.

Other naturally-occurring sulfonium species are S-methylmethionine (methioninium) and the related dimethylsulfoniopropionate (DMSP).

Organic synthesis

Sulfonium salts are precursor to sulfur ylides, which are useful in carbon–carbon bond-forming reactions. In a typical application, a R2S+CH2R′ center is deprotonated to give the ylide R2S+CHR−.[9]

Structure of tris(dimethylamino)sulfonium difluorotrimethylsilicate.

Tris(dimethylamino)sulfonium difluorotrimethylsilicate [((CH3)2N)3S]+[F2Si(CH3)3]− is a popular fluoridation agent.[10]

Some azo dyes are modified with sulfonium groups to give them a positive charge. The compound

triphenylsulfonium triflate is a photoacid
, a compound that under light converts to an acid.

See also

  • Onium compounds

References

  1. doi:10.1139/v94-238
    .
  2. ISBN 9780470771655
    .
  3. ^
    PMID 32742188
    .
  4. S2CID 20782786
    .
  5. ISBN 0-471-60180-2
  6. ISBN 9780125077040
    .
  7. doi:10.1016/j.cbpa.2004.08.001
  8. doi:10.1021/cr020422m
  9. doi:10.15227/orgsyn.054.0027
    .
  10. doi:10.15227/orgsyn.064.0221
    .

External links
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