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.[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 Template:Chem2. It consists of two electron-withdrawing components, the chlorosulfonyl group (SO2Cl) and the isocyanate group (Template:Chem2). 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:
- Cycloaddition to alkynes to give 1,2,3-oxathiazine-2,2-dioxide-6-chlorides.
- Conversion of primary alcohols to carbamates.[6]
- Conversion of carboxylic acids and the acid chlorides into nitriles.
- Preparation of N,N-disubstituted sulfamides, R2NSO2NH2
- Preparation of Burgess reagent
Safety considerations
CSI is toxic, corrosive and reacts violently with water.
References
- ↑ Graf, R. "Chlorosulfonyl Isocyanate" Organic Syntheses, Collected Volume 5, pages 226ff.
- ↑ 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.
- ↑ D. N. Dhar, K. S. K. Murthy "Recent Advances in the Chemistry of Chlorosulfonyl Isocyanate" Synthesis 1986; pages 437-449.
- ↑ Script error: No such module "Citation/CS1".
- ↑ Cremlyn, R. J. “An Introduction to Organosulfur Chemistry” John Wiley and Sons: Chichester (1996). Template:ISBN
- ↑ 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