Chlorosulfonyl isocyanate

Chlorosulfonyl isocyanate
IUPAC name Chlorosulfonyl isocyanate
Other names N-Carbonylsulfamyl chloride Chloropyrosulfonyl isocyanate Sulfuryl chloride isocyanate
Identifiers
CAS number	1189-71-5 Y
PubChem	70918
ChemSpider	64080 Y
Jmol-3D images	Image 1
SMILES ClS(=O)(=O)N=C=O
InChI InChI=1S/CClNO3S/c2-7(5,6)3-1-4 Y Key: WRJWRGBVPUUDLA-UHFFFAOYSA-N Y InChI=1/CClNO3S/c2-7(5,6)3-1-4 Key: WRJWRGBVPUUDLA-UHFFFAOYAX
Properties
Molecular formula	CNClO3S
Molar mass	141.53 g/mol
Appearance	colorless liquid
Density	1.626 g/cm3
Melting point	-44 °C
Boiling point	107 °C
Solubility in water	decomp.
Solubility in other solvents	Chlorocarbons MeCN
Refractive index (nD)	1.447
Structure
Molecular shape	tetrahedral at S
Hazards
Main hazards	toxic, corrosive hydrolyzes violently
Related compounds
Related compounds	Thionyl chloride Cyanogen bromide Phosphoryl chloride
Y isocyanate (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Chlorosulfonyl isocyanate is the chemical compound ClSO₂NCO, known as CSI. This compound is a versatile reagent in organic synthesis.

Preparation, structure, handling

CSI is prepared by treating cyanogen chloride with sulfur trioxide, the product being distilled directly from the reaction mixture.^[1]

SO₃ + ClCN → ClSO₂NCO

In this transformation, both the carbon and the nitrogen termini of CN are functionalized.

The structure of CSI is represented as ClS(O)₂-N=C=O. It consists of two electron-withdrawing components, the chlorosulfonyl group (SO₂Cl) and the isocyanate group (-N=C=O). Because of its resulting electrophilicity, the use of CSI in chemical synthesis requires relatively inert solvents such as chlorocarbons, acetonitrile, and ethers.^[2]

Uses

The molecule has two electrophilic sites, the carbon and the S(VI) center.^[3]

CSI has been employed for the preparation of β-lactams, some of which are medicinally important. Thus, alkenes undergo a [2+2]-cycloaddition to give the sulfonamide. The SO₂Cl group can be removed simply by hydrolysis, leaving the secondary amide.^[4] Other reactions of CSI:

• Cycloaddition to alkynes to give 1,2,3-oxathiazine-2,2-dioxide-6-chlorides.
• Conversion of primary alcohols to carbamates.^[5]
• Conversion of carboxylic acids and the acid chlorides into nitriles.
• Preparation of N,N-disubstituted sulfamides, R₂NSO₂NH₂

Safety considerations

CSI is toxic, corrosive and reacts violently with water. It cannot be stored in glass-stoppered flasks, requiring instead polyethylene bottles.

References

1. ^ Graf, R. "Chlorosulfonyl Isocyanate" Organic Syntheses, Collected Volume 5, pages 226ff.
2. ^ Miller, M. J.; Ghosh, M.; Guzzo, P. R.; Vogt, P. F.; Hu, J.; Filzen, G. F.; Geyer, A. G. "Chlorosulfonyl Isocyanate" in "Encyclopedia of Reagents for Organic Synthesis" 2005 John Wiley & Sons: New York.
3. ^ D. N. Dhar, K. S. K. Murthy "Recent Advances in the Chemistry of Chlorosulfonyl Isocyanate" Synthesis 1986; pages 437-449.
4. ^ Cremlyn, R. J. “An Introduction to Organosulfur Chemistry” John Wiley and Sons: Chichester (1996). ISBN 0-471-95512-4
5. ^ Burgess, E. M.; Penton, Jr., H. R.; Taylor, E. A.; Williams, W. M. "Conversion of Primary Alcohols to Urethanes via the Inner Salt of Triethylammonium Hydroxide: Methyl (Carboxylsulfamoyl) Triethylammonium Hydroxide Methyl n-Hexylcarbamate" Organic Syntheses, Coll. Vol. 6, p.788