Methyl sulfoxide purification

Purification of the crude mixture was performed by flash chromatography to afford pure 5-(l-hydroxyethyl)-2-methyl-3-furoic acid 5a-cholestan-3(3-yl ester (4) (90 % yield) and (R)-4-bromophenyl methyl sulfoxide (3) (61 % yield). 

Solvents that have been less extensively used are N-methyl-2-pyrrolidinone and hexamethylphosphoric triamide.183 The author of this article183 also discussed the purification of chlorotrimethylsilane, and the anomalous results that may be obtained from the use of impure reagent have been commented on in the case of analyses of pentaerythritol.184 The various methods available for the bulk purification of methyl sulfoxide have been reviewed,185 and a symposium on this compound reviewed its use as a solvent in selected reactions.186... 

Various ratios of AA, IA and NVP monomers were copolymerized in water with potassium persulfate initiator ( 2 % by wt of combined monomers) with polymerization run under nitrogen for 9-10 hr at 95 °C. The copolymers prepared (Table 2) were recovered in high yields, using standard freeze-drying techniques. Several poly(AA-co-lA) and poly(AA-co-NVP) were also prepared for the study. For purification, the copolymers were dissolved in methyl alcohol and precipitated from diethyl ether, followed by drying under vacuum. The IR spectrum of the copolymers were obtained from cast films, using a MID AC FT IR Spectrometer. NMR ( H and C) spectra were obtained on a Bruker AM 250 MHz NMR analyzer, using deutrated methyl sulfoxide solvent and trimethylsilane (TMS) reference (Table I). 

To a solution of 1 equiv of( + )-(R)-methyl 4-tolyl sulfoxide (1) inTHF is added a solution of 1 equiv of LDA at 0°C and, after cooling to —78 C, a solution of 1 equiv of an appropriate imine 2. Addition is usually complete within 10 min. The reaction is quenched with dilute HCI, extracted with CH,C12 and the extracts are dried and evaporated. The products are purifed by Hash chromatography (silica gel). The main diastcreomer can be isolated by crystallization from cyclohexane. No further preparative details are available. 

Preparation of various enantiomerically pure sulfoxides by oxidation of sulfides seems feasible in the cases where asymmetric synthesis occurs with ee s in the range of 90% giving crystalline products which can usually be recrystallized up to 100% ee. Aryl methyl sulfides usually give excellent enantioselectivity during oxidation and are good candidates for the present procedure. For example, we have shown on a 10-mmol scale that optically pure (S)-(-)-methyl phenyl sulfoxide [a]p -146 (acetone, o 1) could be obtained in 76% yield after oxidation with cumene hydroperoxide followed by flash chromatographic purification on silica gel and recrystallizations at low temperature in a mixed solvent (ether-pentane). Similarly (S)-(-)-methyl o-methoxyphenyl sulfoxide, [a]p -339 (acetone, o 1.5 100% ee measured by HPLC), was obtained in 80% yield by recrystallizations from hexane. 

Chemicals and Standard Solutions. Cyclohexanone, cyclohexanol, 1,3,5-trichlorobenzene, 1,2,4-trichlorobenzene, phenol, 4-methylphenol, 4-chloro-phenol, 1,2,3,4-tetrahydroisoquinoline, 1-chlorohexane, 1-chlorododecane, and 1-chlorooctadecane were obtained from Aldrich. Acetone, tetrahydrofuran, ethyl acetate, toluene, dimethyl sulfoxide, and methanol were obtained from J. T. Baker. Distilled-in-glass isooctane, methylene chloride, ethyl ether, and pentane were obtained from Burdick and Jackson. Analytical standard kits from Analabs provided methyl ethyl ketone, isopropyl alcohol, ethanol, methyl isobutyl ketone, tetrachloroethylene, dodecane, dimethylformamide, 1,2-dichlorobenzene, 1-octanol, nitrobenzene, 2,4-dichlorophenol, and 2,5-dichlorophenol. All chemicals obtained from the vendors were of the highest purity available and were used without further purification. High-purity water... 

A similar enzyme has been purified 26-fold from the bacterium Pseudomonas cruciviae (53). It shows a constant ratio (about three) between activity on S-methyl-L-cysteine and on the sulfoxide through purification. It cleaves a wide range of S-alkyl and S (2-carboxyalkyl) cysteines but not L-cysteine itself (or other amino acids). 

Octadecylmethyl sulfoxide (OMS) was prepared in the following manner 15 g of octadecyl bromide and 3.5 g of thiourea were dissolved in 150 cm3 of ethanol. The mixture was refluxed for 1 hr after which 100 cm3 of ethanol were removed by distillation. The residue, after cooling, was made alkaline by an ethanol/sodium hydroxide solution (5 g sodium hydroxide in a minimum volume of ethanol). Methyl iodide, 3.7 g, was then added, and the mixture was left to stand overnight. The resulting thioether was recovered by filtration and washed with cold ethanol. The thioether was dissolved in glacial acetic acid then small quantities of 20 vol % hydrogen peroxide, constituting the stoichiometric amount, were added over several hours. The product was precipitated with water, and the precipitate was collected by filtration. The crude product was washed successively with water, ice-cold ethanol, and a small quantity of diethyl ether it was finally dried at 70°C. OMS was purified by successive recrystallization from benzene purification was... 

All the chemicals were commercially obtained and used without further purification. PET bottles of Spritzer (Malaysia) mineral water were shredded into flakes. Sodium hydroxide AR (Chem.AR), Ethylene glycol (Aldrich Chem. Co.) and sulphuric acid (MaUinckrodt Chem. Co.) were used as purchased. Aniline, p-iodoaniline, p-bromoaniUne and p-chloroaniline were purchased from (Aldrich Chem. Co.). 2,5-dihydroxybenzaldehyde, absolute ethanol, methanol, 1-butanol, dimethyl-sulfoxide (DMSO), ethyl methyl ketone and diethyl ether (Fluka Chem. Co.). 

Materials. Dichloromethane and chloroform were purchased from Tokyo Kasei Co., and distilled twice in the usual manner. Methyl phenyl sulfide was purchased from Tokyo Kasei Co. and methyl phenyl sulfoxide was obtained by the oxidation of the methyl phenyl sulfide. Trifiuoromethanesulfonic acid, and pyridine were purchased from Tokyo Kasei Co. Ltd. and used without further purification. 

Methyl aryl sulfides are converted in a mild, one-pot, three-step procedure via Pummerer rearrangement of the corresponding sulfoxides, and without purification of intermediates, to provide arylthiols in excellent yields (eq 11). ... 

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