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Chlorosulfonyl isocyanate (CSI, CAS 1189-71-5) combines the most reactive known isocyanate group with a sulfonyl chloride in one small molecule, making it one of the most versatile electrophilic reagents in organic synthesis. Its signature reaction — [2+2] cycloaddition with alkenes to form β-lactam rings — makes it an essential reagent in the manufacture of cephalosporin antibiotics such as cefuroxime and cefoxitin, alongside broad use in sulfamide and sulfamoyl chemistry. Royalchem Spain supplies it at ≥ 99% purity as a colourless transparent liquid, delivered from our Valladolid distribution hub in moisture-tight steel drums.
| Assay (GC) | ≥ 99.0% |
| Appearance | Colourless transparent liquid |
| Total Impurities | ≤ 0.6% |
| Molecular Weight | 141.53 g/mol |
| Density (20 °C) | 1.626 g/mL |
| Boiling Point | ≈ 107 °C |
| Melting Point | ≈ −44 °C |
An essential reagent in the industrial synthesis of cefuroxime, cefoxitin, and other second- and third-generation cephalosporins, introducing the carbamoyl group and enabling β-lactam ring construction in antibiotic manufacture.
The reagent of choice for stereoselective [2+2] cycloadditions with alkenes and dienes to give N-chlorosulfonyl-β-lactams — a direct route to novel β-lactam scaffolds, nitrogen heterocycles, and nitrile syntheses in medicinal chemistry.
A bifunctional electrophile for sulfamoyl carbamates, N,N-disubstituted sulfamides, and sulfonyl-based bioisosteres used in drug discovery, plus applications in agrochemical and specialty-chemical synthesis.
Standard Packaging:
Moisture-tight steel drums (e.g. 250 kg) under dry nitrogen — or to customer requirement. Distributed by Royalchem Spain from our Valladolid hub. Shelf life 12 months in original sealed packaging kept strictly dry.
Storage Conditions:
Store in tightly sealed containers under dry nitrogen in a cool, dry, well-ventilated corrosives store, strictly away from water, moisture, alcohols, amines, and bases — CSI reacts violently with water, releasing HCl. Keep equipment and transfer lines scrupulously dry.