Chlorosulfonyl isocyanate


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.
In this transformation, both the carbon and the nitrogen termini of CN are functionalized.
The structure of CSI is represented as ClS2-N=C=O. It consists of two electron-withdrawing components, the chlorosulfonyl group and the isocyanate group. 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 center.
CSI has been employed for the preparation of β-lactams, some of which are medicinally important. Thus, alkenes undergo a -cycloaddition to give the sulfonamide. The SO2Cl group can be removed simply by hydrolysis, leaving the secondary amide.
Other reactions of CSI:
CSI is toxic, corrosive and reacts violently with water. Like hydrofluoric acid, it cannot be stored in glassware, requiring instead polyethylene bottles.