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

organic synthesis Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...

Preparation, structure, handling

CSI is prepared by treating

cyanogen chloride Cyanogen chloride is an inorganic compound with the formula . This triatomic pseudohalogen is an easily condensed colorless gas. More commonly encountered in the laboratory is the related compound cyanogen bromide, a room-temperature solid that is ...

with

sulfur trioxide Sulfur trioxide (alternative spelling sulphur trioxide) is the chemical compound with the formula SO3. It has been described as "unquestionably the most conomicallyimportant sulfur oxide". It is prepared on an industrial scale as a precursor to ...

, 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 . It consists of two electron-withdrawing components, the chlorosulfonyl group (SO₂Cl) and the

isocyanate In organic chemistry, isocyanate is the functional group with the formula . Organic compounds that contain an isocyanate group are referred to as isocyanates. An organic compound with two isocyanate groups is known as a diisocyanate. Diisocyan ...

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(VI) center. CSI has been employed for the preparation of β-

lactam A lactam is a Cyclic compound, cyclic amide, formally derived from an amino alkanoic acid through cyclization reactions. The term is a portmanteau of the words ''lactone'' + ''amide''. Nomenclature Greek_alphabet#Letters, Greek prefixes in alpha ...

s, some of which are medicinally important. Thus, alkenes undergo a +2/nowiki>-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

carbamate In organic chemistry, a carbamate is a category of organic compounds with the general Chemical formula, formula and Chemical structure, structure , which are formally Derivative (chemistry), derived from carbamic acid (). The term includes orga ...

s.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 *Conversion of

carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...

s and the acid chlorides into

nitrile In organic chemistry, a nitrile is any organic compound that has a functional group. The name of the compound is composed of a base, which includes the carbon of the , suffixed with "nitrile", so for example is called " propionitrile" (or pr ...

s. *Preparation of N,N-disubstituted sulfamides, R₂NSO₂NH₂ *Preparation of

Burgess reagent The Burgess reagent (methyl ''N''-(triethylammoniumsulfonyl)carbamate) is a mild and selective dehydrating reagent often used in organic chemistry. It was developed in the laboratory of Edward M. Burgess at Georgia Tech. The Burgess reagent is u ...

Safety considerations

CSI is toxic, corrosive and reacts violently with water.

References

{{carbon compounds Inorganic carbon compounds Reagents for organic chemistry Isocyanates Sulfuryl compounds