Chlorosulfonyl isocyanate

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

Chlorosulfonyl isocyanate
Names
IUPAC name
Chlorosulfonyl isocyanate
Other names
N-Carbonylsulfamyl chloride
Chloropyrosulfonyl isocyanate
Sulfuryl chloride isocyanate
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.013.378
EC Number
  • 214-715-2
UNII
Properties
CNClO3S
Molar mass 141.53 g/mol
Appearance colorless liquid
Density 1.626 g/cm3
Melting point −44 °C (−47 °F; 229 K)
Boiling point 107 °C (225 °F; 380 K)
decomposition
Solubility in other solvents Chlorocarbons
MeCN
1.447
Structure
tetrahedral at S
Hazards
Main hazards toxic, corrosive, flammable,
reacts violently with water
Safety data sheet "External MSDS"
GHS pictograms
GHS Signal word Danger
H302, H312, H314, H330, H332, H334
P260, P261, P264, P270, P271, P280, P284, P285, P301+312, P301+330+331, P302+352, P303+361+353, P304+312, P304+340, P304+341, P305+351+338, P310, P312, P320, P321, P322, P330, P342+311, P363, P403+233
NFPA 704 (fire diamond)
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazard W: Reacts with water in an unusual or dangerous manner. E.g. sodium, sulfuric acid
1
3
2
Related compounds
Related compounds
 Thionyl chloride
Cyanogen bromide
Phosphoryl chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

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,[4] 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.[5] Other reactions of CSI:

Safety considerations

CSI is toxic, corrosive and reacts violently with water. Like hydrofluoric acid, it cannot be stored in glassware, 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. Kaur, Rajneesh; Singh, Raman; Kumar, Antresh; Kaur, Satvinder; Priyadarshi, Nitesh; Singhal, Nitin Kumar; Singh, Kuldeep (June 2020). "1,2,3-Triazole β-lactam conjugates as antimicrobial agents". Heliyon. 6 (6): e04241. doi:10.1016/j.heliyon.2020.e04241. PMC 7327255. PMID 32637684.
  5. Cremlyn, R. J. “An Introduction to Organosulfur Chemistry” John Wiley and Sons: Chichester (1996). ISBN 0-471-95512-4
  6. 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
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