[15963-66-3]  · C12H16ClNO2S  · N-Chloro-N-cyclohexylbenzenesulfonamide  · (MW 273.78)

(used for radical chlorination at allylic1,4 or benzylic carbon1)

Physical Data: mp 42 °C.

Solubility: sol benzene, CCl4, CHCl3, CH2Cl2; insol H2O, petroleum ether.

Analysis of Reagent Purity: mp, NMR, combustion analysis.

Preparative Methods: N-cyclohexylbenzenesulfonamide can be prepared by addition of benzenesulfonyl chloride to a solution of cyclohexylamine in pyridine and purified by recrystallization from ethanol. N-Chlorination is accomplished by treating a solution of N-cyclohexylbenzenesulfonamide in dichloromethane with NaOCl solution at 0 °C followed by dropwise addition of glacial acetic acid.1 Alternatively, a suspension of N-cyclohexylbenzenesulfonamide in acetic acid can be treated with NaOCl solution or powdered N-cyclohexylbenzenesulfonamide can be added to a solution containing NaHCO3 and NaOCl.2

Purification: precipitation from CHCl3 solution by addition of petroleum ether or trituration with petroleum ether.

Handling, Storage, and Precautions: to avoid decomposition, this reagent should be protected from prolonged exposure to light and moisture. Store under nitrogen in the dark. This toxic reagent should be handled in a fume hood.

Allylic Chlorination.

This reagent (1) has been used as a chlorine source in radical chlorination of allylic and benzylic positions. Treatment of alkenes bearing allylic carbon-hydrogen bonds with (1) in refluxing benzene in the presence of a radical initiator such as Dibenzoyl Peroxide results in the formation of allyl chlorides in good to moderate yields (eq 1).1

As with the more commonly used chlorinating agent N-Chlorosuccinimide, this chlorination proceeds via a radical chain reaction in which Cl2 is liberated and reacts with a carbon radical.3 Consequently, isomeric mixtures are often obtained (eqs 2-4).1,4

Separation of the resulting isomeric products is often difficult. For example, the isomeric chlorinated products in eq 4 were separated from one another using preparative gas chromatography.4 N-Cyclohexylbenzenesulfonamide precipitates upon cooling of the reaction mixture and can be recovered by filtration.1

Chlorination at benzylic positions proceeds in good yields (eq 5).1

Related Reagents.

t-Butyl Hypochlorite; N-Chlorosuccinimide; Hypochlorous Acid; Phenylselenium Trichloride.

1. Theilacker, W.; Wessel, H. LA 1967, 703, 34.
2. Yuki, H.; Kishikawa, T.; Tohira, Y.; Suzuki, S.; Sano, F.; Hayakawa, S. CPB 1967, 15, 1123.
3. Dauben, H. J.; McCoy, L. L. JACS 1959, 81, 4863.
4. Cristol, S. J.; Daughenbaugh, R. J. JOC 1979, 44, 3434.

George D. Maynard

Marion Merrell Dow, Cincinnati, OH, USA

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