Organic thiocyanates

Source: Wikipedia, the free encyclopedia.
Phenyl thiocyanate and phenyl isothiocyanate are isomers.

Organic thiocyanates are organic compounds containing the functional group RSCN. the organic group is attached to sulfur: R−S−C≡N has a S–C single bond and a C≡N triple bond.[1]

Organic thiocyanates are valued building blocks. They allow to access efficiently various sulfur containing functional groups and scaffolds.[2]

Synthesis

Several synthesis routes exist,

isopropyl bromide with sodium thiocyanate in boiling ethanol.[5]
The main complication with this route is the competing formation of alkyisothiocyanates. "SN1-type" substrates (e.g., benzyl halides) tend to give the isothiocyanate derivatives.

Some organic thiocyanates are generated by

organosulfur compounds. Sulfenyl thiosulfates (RSSO3−) react with alkali metal cyanides to give thiocyanates with displacement of sulfite. This approach has been applied to allyl thiocyanate:[6]

CH2=CHCH2Cl + Na2S2O3 → CH2=CHCH2S2O3Na + NaCl
CH2=CHCH2S2O3Na + NaCN → CH2=CHCH2SCN + Na2SO3

Sulfenyl chlorides (RSCl) also convert to thiocyanates.

Aryl thiocyanates are traditionally produced by the

diazonium salts:[3]

[ArN2]BF4 + CuSCN → ArSCN + CuBF4 + N2

Some arylthiocyanates can also often be obtained by thiocyanogenation, i.e. the reaction of thiocyanogen. This reaction is favored for electron-rich aromatic substrates.[1]

Structure

In

pm in isothiocyanate]s.[7]

Typical

bond angles for C−S−C are 100°.[3]
By contrast C−N=C in aryl isothiocyanates is 165°. Again, the thiocyanate isomers are quite different with C−S−C angle near 100°.

In both organic thiocyanate and isothiocyanate isomers the SCN angle approaches 180°.

Reactions

Organic thiocyanates are hydrolyzed to thiocarbamates in the Riemschneider thiocarbamate synthesis.

Some thiocyanates isomerize to the isothiocyandates. This reaction is especially rapid for the allyl isothiocyanate:[6]

CH2=CHCH2SCN → CH2=CHCH2NCS

See also

References

  1. ^
    ISBN 9780470771532
    .
  2. PMID 26658383
    .
  3. ^
    doi:10.1016/S0040-4020(99)00386-5
    .
  4. ^ "Synthesis of thiocyanates".
  5. doi:10.15227/orgsyn.011.0092
    .
  6. ^
    doi:10.1021/ed048p81
    .
  7. doi:10.1016/j.chemphys.2008.10.024
    .
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