[6209-71-8] · C12H8N2O10S2 · m-Nitrobenzenesulfonyl Peroxide · (MW 404.36)
Alternate Name: m-NBSP.
Physical Data: mp 107 °C (dec); decomposition at the melting point is exothermic.
Solubility: (>1 g 100 mL-1) ethyl acetate, acetone, acetonitrile; slightly sol dichloromethane, diethyl ether, chloroform; insol pentane, water.
Form Supplied in: off-white or pale yellow powder.
Analysis of Reagent Purity: purity is determined by iodometric titration. A weighed quantity (70 mg) of the peroxide is dissolved in ethyl acetate (20 mL) and treated with glacial acetic acid (10 mL) and 10% potassium iodide (10 mL). The solution is titrated to a starch endpoint with standardized thiosulfate (~0.01 N).
Preparative Method: m-nitrobenzenesulfonyl chloride (11.1 g, 0.05 mol) is dissolved in chloroform (15 mL) and added with stirring to a cold (-20 °C) solution of Potassium Carbonate (8.5 g) in water (140 mL), ethanol (70 mL), and 30% Hydrogen Peroxide (20 g) in a Waring blender cup. Agitation is slowly increased to full power and held there for 1 min. Ethanol (100 mL), is then added and the mixture is agitated slowly for a few minutes. The resulting precipitate is collected by filtration, washed thoroughly with water, and dried under vacuum.
Purification: the crude product is dissolved in acetone at room temperature, the solution is filtered, and the filtrate is concentrated under reduced pressure to yield 97% pure peroxide (5.0 g, 49%) which decomposes at 107 °C.2,3
Handling, Storage, and Precautions: can be stored at -20 °C for a considerable time without loss of purity. Plastic spatulas are recommended for transfer. It can decompose vigorously in the presence of electron donors,3 and should only be handled with suitable protection. Use in a fume hood.
Being a strong electrophile, m-nitrobenzenesulfonyl peroxide reacts readily with good electron donors. This reactivity has been exploited in several useful synthetic processes. Heteroatom oxidations, aromatic substitutions, and additions to unactivated alkenes have been reported. In addition m-nitrobenzenesulfonyloxy radicals can be produced homolytically.
m-NBSP reacts with diselenides,4 ditellurides,5 and disulfides5 to generate electrophilic intermediates (1) (eq 1), which react with alkenes in the presence of various nucleophiles to give addition products (2) (eq 2).
The intermediate (1) initiates the electrophilic cyclization of unsaturated alcohols to form cyclic ethers and can be used for phenylsulfolactonization or phenylselenolactonization of unsaturated carboxylic acids to lactones (eq 3).4,5 Selenium works particularly well in these reactions. Furthermore, intermediate (1) (X = Se) is sufficiently electrophilic to react with aromatic compounds such as anisole, phenol, acetanilide, and toluene to produce benzeneselenated aromatic products in variable yields (12-94%).4b
The reaction of m-NBSP with the nitrogen atom of substituted benzylamines has been used to produce N-[(m-nitrobenzenesulfonyl)oxy]benzylamines, which undergo base induced elimination to imines.6 It has also been reported that O-(m-nitrobenzenesulfonyl) hypochlorites and O-(m-nitrobenzenesulfonyl) hypobromites formed by the reaction of m-NBSP with chloride and bromide ions, respectively, are effective reagents for the electrophilic halogenation of aromatic rings (50-93%).7
m-NBSP reacts with methyl benzoate, anisole, nitrobenzene, halobenzenes, and alkylbenzenes (as well as many other aromatic compounds) to give aryl m-nitrobenzenesulfonates (3) (eq 4).1 Hydrolysis or reductive cleavage of these products gives phenols.8 Attempted oxygenation of toluene failed in the presence of salts known to catalyze radical reactions.9
Decomposition of m-NBSP in chloroform solution gives m-nitrobenzenesulfonic acid (eq 5), in addition to hexachloroethane and phosgene.10 The same process is also found for other arylsulfonyl peroxides and constitutes an excellent method for the preparation of arylsulfonic acids.11 Activation parameters and the reaction products indicate that the decomposition in chloroform proceeds by homolytic cleavage of the O-O bond.10
m-NBSP undergoes electrophilic addition to alkenes such as norbornene and gives syn-7-(arylsulfonyloxy)norbornene and 2,7-bis(arylsulfonyloxy)norbornane. Norbornadiene reacts with m-NBSP to give arylsulfonyloxytricycloheptane products.12
Naresh K. Nayyar & Robert V. Hoffman
New Mexico State University, Las Cruces, NM, USA