Benzenesulfonyl Bromide

[2297-65-6]  · C6H5BrO2S  · Benzenesulfonyl Bromide  · (MW 221.07)

(used as a sulfonating reagent to produce sulfonamides2-4 and sulfones5-8)

Physical Data: mp 19.5 °C; bp 76-78 °C/0.17 mmHg.

Solubility: sol CH2Cl2, Et2O, THF, C6H6, MeCN.

Preparative Method: prepared by reaction of sodium benzenesulfonate with bromine in 98% yield.1

Handling, Storage, and Precautions: by analogy to Benzenesulfonyl Chloride, benzenesulfonyl bromide should be assumed to be an irritant and harmful by skin absorption and ingestion. Benzenesulfonyl bromide is best used immediately following preparation and may be used in situ. The reagent is moisture sensitive and will react with nucleophilic solvents (e.g. alcohols), liberating HBr and therefore should be stored under an inert atmosphere. Use in a fume hood.

Protection of Nitrogen; Formation of Sulfonamides.

Unlike the corresponding arenesulfonyl chlorides (see Benzenesulfonyl Chloride and p-Toluenesulfonyl Chloride), benzenesulfonyl bromide has been used much less extensively in organic synthesis. Primary amines2 and imidazoles (eq 1)3 have been converted to the corresponding benzenesulfonamides and, with indoles, bromination at C-3 occurs with concomitant sulfonamide formation (eq 2).4

Addition to Unsaturated Compounds.

Benzenesulfonyl bromide undergoes radical-mediated addition to alkenes and alkynes. Addition to alkenes leads to bromo sulfones, which undergo dehydrobromination to give vinyl sulfones (eq 3).5

Addition to vinyl ethers and vinyl esters is regioselective, leading to the corresponding b-alkyloxy/acyloxy sulfone.6 Addition to alkynes gives vinyl sulfones via a radical pathway. These reactions can be carried out in the presence of peroxide initiators,7 with Lewis acids such as Copper(II) Bromide (eq 4),8 or thermally (eq 5).8,9

With enynes, mixtures of addition products resulting from 1,2- and 1,4-addition have been observed.10,11 Radical addition with tricyclic alkanes has also been observed.12

Reaction with Arenes.

Benzenesulfonyl bromide reacts readily with trifluoromethanesulfonyl derivatives, yielding the corresponding mixed anhydrides (eq 6)13 which have been used to convert arenes to aryl phenyl sulfones under Friedel-Crafts-type conditions.


1. Cristol, S. J.; Harrington, J. K.; Singer, M. S. JACS 1966, 88, 1529.
2. Belousova, I. A.; Savelova, V. A.; Litvinenko, L. M.; Matvienko, V. N. ZOR 1979, 15, 1947.
3. Litvinenko, L. M.; Zaslavskii, V. G.; Savelova, V. A.; Dadali, V. A.; Simanenko, Y. S.; Solomoichenko, T. N. ZOR 1976, 12, 1945.
4. Dalton, L.; Humphrey, G. L.; Cooper, M. M.; Joule, J. A. JCS(P1) 1983, 2417.
5. Doomes, E.; Clarke, U.; Neitzel, J. JOC 1987, 52, 1540.
6. Kalabina, A. V.; Vasil'eva, M. A.; Bychkova, T. I. ZOR 1979, 15, 268.
7. Böll, W. LA 1979, 1665.
8. Amiel, Y. JOC 1974, 39, 3867.
9. Pelter, A.; Ward, R. S.; Little, G. M. JCS(P1) 1990, 2775.
10. Bez"Yazychnaya, L. A.; Stadnichuk, M. D. ZOB 1976, 46, 1557.
11. Stadnichuk, M. D.; Kryukova, T. B.; Petrov, A. A. ZOB 1975, 45, 838.
12. Vasin, V. A.; Bolusheva, I. Y.; Chernyaeva, L. A.; Tanaseichuk, B. S.; Surmina, L. S.; Zefirov, N. S. ZOR 1990, 26, 1509.
13. Effenberger, F.; Huthmacher, K. CB 1976, 109, 2315.

Stephen Thompson

University of Bristol, UK



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