m‐Nitrobenzenesulfonyl Peroxide

[6209-72-9] C12H8N2O10S2 (MW 404.36) InChI = 1S/C12H8N2O10S2/c15-13(16)9-1-5-11(6-2-9)25(19,20)23-24-26(21,22)12-7-3-10(4-8-12)14(17)18/h1-8H InChIKey = PIYAGWBMKPQDOX-UHFFFAOYSA-N (oxygen electrophile for addition to unsaturated compounds;1 preparation of α-nosyloxy ketones and esters;3 addition to 1-alkoxy-1-silyloxy-1,3-dienes;6 addition to enols3 to give tricarbonyl esters and amides;3 addition to amines to give N-nosyloxyamines1) Alternate Name: p-NBSP. Physical Data: mp 128 °C (dec); decomposition at the melting point is exothermic; typical preparations with mp >124 °C are generally satisfactory. Solubility: sol (>1 g 100 mL−1) ethyl acetate, acetone, acetonitrile; slightly sol dichloromethane, ether, chloroform; insol pentane, water. Form Supplied in: off-white or pale yellow powder; typical impurities are p-nitrobenzenesulfonic acid and water. 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: prepared by the addition of p-nitrobenzenesulfonyl chloride (20 g) in chloroform (40 mL) to a −20 °C solution of Potassium Carbonate (15.6 g) and 30% Hydrogen Peroxide in 2∶1 water–ethanol (360 mL).2 The mixture is agitated in a chilled Waring Blender cup at full power for 1.5 min. The mixture is filtered on a large Buchner funnel and the oily solid is washed copiously several times with water. A good washing protocol is to suspend the solid in water and stir in the Waring Blender at medium power for 1 min and refilter. The faintly yellow solid is dried by passing air through the solid on the filter, and then in vacuo at room temperature. It is prudent to use plastic implements when manipulating the peroxide. Purification: the crude peroxide is dissolved in reagent grade acetone (360 mL), the solution is cooled to −78 °C, and a vigorous stream of air is directed onto the surface of the stirred solution. When the volume has been reduced to 180 mL, the mixture is filtered and air is passed through the solid until it is completely dry. Purities of >97% normally result if care is taken to completely dry the peroxide when it is first isolated. Yields of 40–50% of purified product are normal. An alternate method of purification which delivers material suitable for most purposes (>95% purity) is to suspend the peroxide in acetone (150 mL) and stir at −78 °C for 1.5–2 h. Filtration and air drying give acceptable product. It is even more crucial that the crude product be quite dry before using this procedure as the major impurity seems to be water that is not easily removed by this method of purification. Handling, Storage, and Precautions: can be stored for long periods of time at −20 °C without loss of purity and can be handled in the laboratory using normal laboratory procedures and precautions. Plastic spatulas are recommended for transfer. Vigorous reaction occurs with neat or concentrated solutions of good electron donors such as amines, alkenes, or alkoxides, but p-NBSP is relatively stable towards oxygen, water, acids, and a variety of common solvents such as acetone, ethyl acetate, dichloromethane, and acetonitrile. Because p-NBSP can decompose exothermically (but not explosively), personal protection in the form of eye protection, gloves, etc. is necessary when handling the peroxide.