Chlorosulfonyl isocyanate

Chlorosulfonyl isocyanate
Chlorosulfonyl isocyanate Chlorosulfonyl isocyanate
General
Systematic name	Chlorosulfonyl isocyanate
Other names	N-Carbonylsulfamyl chloride Isocyanic acid, anhydride chloropyrosulfonyl isocyanate
Molecular formula	CNClO3S
SMILES	ClS(=O)(=O)\N=C=O
Molar mass	141.53 g/mol
Appearance	colorless liquid
CAS number	[1189-71-5]
Properties
Density and phase	1.626 g/cm3
Solubility in water	decomp.
Other solvents	Chlorocarbons</br>MeCN
Melting point	-44 °C
Boiling point	107 °C
Structure
Molecular shape	tetrahedral at S
Dipole moment	? D
Hazards
MSDS	External MSDS
Main hazards	toxic, corrosive hydrolyzes violently
NFPA 704	1 3 1
R/S statement	R: 14-22-34-42 S: 23-26-30-36/37/39-45
RTECS number	?
Supplementary data page
Structure and properties	n, 1.447
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Related compounds	SOCl2</br> BrCN, POCl3
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and 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.

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.

Uses

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

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. Other reactions of CSI:

• Cycloaddition to alkynes to give 1,2,3-oxathiazine-2,2-dioxide-6-chlorides.
• Conversion of primary alcohols to urethanes.
• 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.

External links

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