Dimethyldioxirane (2005)

[74087-85-7] C3H6O2 (MW 74.09) InChI = 1/C3H6O2/c1-3(2)4-5-3/h1-2H3 InChIKey = FFHWGQQFANVOHV-UHFFFAOYSA-N (selective, reactive oxidizing agent capable of epoxidation of alkenes and arenes,11 oxyfunctionalization of alkanes,19 and oxidation of alcohols,23 ethers,21 amines, imines,32 and sulfides35) Alternate Name: DDO. Physical Data: known only in the form of a dilute solution. Solubility: soluble in acetone and CH2Cl2; soluble in most other organic solvents, but reacts slowly with many of them. Form Supplied in: dilute solutions of the reagent in acetone are prepared from Oxone and acetone, as described below. Analysis of Reagent Purity: the concentrations of the reagent can be determined by classical iodometric titration or by reaction with an excess of an organosulfide and determination of the amount of sulfoxide formed by NMR or gas chromatography. Preparative Methods: the discovery of a convenient method for the preparation of dimethyldioxirane has stimulated important advances in oxidation technology.1 The observation2 that ketones enhance the decomposition of the monoperoxysulfate anion prompted mechanistic studies that implicated dioxiranes as intermediates.3 Ultimately, these investigations led to the isolation of dilute solutions of several dioxiranes.4 DDO is by far the most convenient of the dioxiranes to prepare and use (eq 1). Several experimental set-ups for the preparation of DDO have been described,4-6 but reproducible generation of high concentration solutions of DDO (ca 0.1M) is aided by a well-formulated protocol.6 The procedure involves the portionwise addition of solid Oxone (Potassium Monoperoxysulfate) to a vigorously stirred solution of NaHCO3 in a mixture of reagent grade Acetone and distilled water at 5–10 °C. The appearance of a yellow color signals the formation of DDO, at which point the cooling bath is removed and the DDO–acetone solution is distilled into a cooled (−78 °C) receiving flask under reduced pressure (80–100 Torr). After preliminary drying over reagent grade anhydrous MgSO4 in the cold, solutions of DDO are stored over molecular sieves in the freezer of a refrigerator at −10 to −20 °C. In instances where the concentration of DDO is crucial, analysis is typically based on reaction with an excess of an organosulfide monitored by NMR.4, 7, 8 (1) Concentrated solutions of DDO in chlorinated solvents may be obtained by a simple extraction technique. A fresh solution (50 mL) of isolated DDO (0.06–0.08 M in acetone), prepared as reported, is diluted with an equal volume of cold water (0–5 °C) and extracted in a chilled separatory funnel with four 10 mL portions of cold CH2Cl2, CHCl3, or CCl4 to yield a total volume of ca. 35 mL of extract (pale yellow DDO solution). In order to concentrate this DDO solution, the combined extracts in chlorinated solvent are washed three times in a separatory funnel at 0–5 °C with an equal volume of cold 0.01 M phosphate buffer (pH 7). The resulting solution is 0.19–0.36 M in DDO. Its concentration can be estimated by iodometry; the recovery of dioxirane from the initial acetone solution is 35–45% in most cases. 1H NMR spectroscopy analysis reveals that initial solvent acetone is not completely eliminated. Handling, Storage, and Precaution: solutions of the reagent can be kept in the freezer of a refrigerator (−10 to −20 °C) for as long as a week. The concentration of the reagent decreases relatively slowly, provided solutions are kept from light and traces of heavy metals. These dilute solutions are not known to decompose violently, but the usual precautions for handling peroxides should be applied, including the use of a shield. All reactions should be performed in a fume hood to avoid exposure to the volatile oxidant.