Trimethylamine oxide dihydrate

Trimethylamine oxide is normally available as a hydrate, and for the present preparation it is necessary to convert it to its anhydrous form. A convenient way of doing this is as follows. A solution of 45.0 g. of trimethylamine oxide dihydrate (supplied by Beacon Chemicals) is dissolved in 300 ml. of warm dimethyl-formamide and placed in a three-necked flask set up for distillation. At atmospheric pressure the flask is heated and solvent distilled off until the boiling point reaches 152-153°. Then the pressure is reduced using a water aspirator, and the remainder of the solvent is distilled. At the end of the distillation the temperature of the bath is slowly raised to 120°. The residual anhydrous trimethylamine oxide (30 g.) can be dissolved in 100 ml. of chloroform and may remain in the same flask for use in the present preparation. 

Aldehyde synthesis [before references], Franzen5 gives a procedure for drying trimethylamine oxide dihydrate (supplied by Beacon Chemicals) by mixing with dimethylformamide and distillation, eventually in vacuum, until the solvent is all removed. A solution of the residue in chloroform is treated with n-octyl iodide, added dropwise with stirring in 20-30 min. After refluxing for 20 min., the solution is cooled and treated with 2 N aqueous sulfuric acid at 50°. The chloroform layer is... 

A mixture of 100 ml. of aqueous 33% trimethylamine solution and 600 ml. of 3% hydrogen peroxide is allowed to stand for 24 hours. If the odor of the amine is still apparent, another 100-200 ml. of hydrogen peroxide is added. After the amine odor has disappeared, the mixture is evaporated under vacuum and the residue is recrystallized from ethanol-ether mixture. The yield of trimethylamine oxide dihydrate, m.p. 96°, is around 95%. 

Oxidation of 1-boraadamantane THF complex 42 with H2O2 in basic media <1979IZV2544> or by trimethylamine iV-oxide dihydrate <2003JA12179, 20010L3063> gave rise to the triol, m, r-l,3,5-tris(hydroxymethyl)cyclohexane 43. The triol 44 was also prepared from the adduct 45 using the first procedure (Scheme 11) <1979IZV2724>. 

Materials. Trimethylamine N-oxide dihydrate (98%) from Aldrich and N-dimethyldodecylamine N-oxide (97%) from Fluka Chemie were used as received. N-dimethylhexylamine N-oxide and N-dimethyloctylamine N-oxide were prepared by reaction of the corresponding tertiary amine with hydrogen peroxide (12). Both samples were isolated as crystalline solids and were >99% pure, based on acid/base titrations and spectrometric methods. Both samples were very hygroscopic. Reagent grade NaBr, 0.1 N and 2.0 N HC1 were from J.T. Baker Chemical Co. and the all solutions were prepared using distilled and deionized water. The pH was monitored using an Orion Ross combination pH electrode and an Orion EA 940 meter. 

To a solution of 30.4 mg (0.114 mmol) of3-bis(phenylsulfonyl)methylcyclopentene in 2.4 mLofdry CH2C12 are added 16.4 mg (0.147 mmol) of trimethylamine iV-oxide dihydrate and a 2.5% solution of 0s04 (0.01 equiv, 0.00728 mL) in CCl4 in order. After stirring for 4 h, direct filtration through a small pad of silica gel (EtOAc elution) and subsequent evaporation of the eluent gives the desired product (91 %) in a 92 8 ratio as determined by H-NMR analysis (CDC13/D20). 

For dehydration 10 g. of the amine oxide dihydrate is placed in a 150-ml. flask which has a long, wide neck. Some boiling chips are added, and the compound is heated in an oil bath under a water pump vacuum of 10-12 mm. A calcium chloride tube is placed between the water pump and the flask. At an oil bath temperature of 120°, the amine oxide dihydrate melts and begins to bubble. The temperature is raised very slowly. After most of the water is off, the temperature of the bath is maintained at 140-150° for 10 minutes. A new calcium chloride tube is placed in the apparatus, and it is again heated under vacuum. At 180° sublimation starts, and anhydrous amine oxide collects in the neck of the flask. The mixture is held at a bath temperature of 190-200° for 1.5 hours to complete the sublimation. The yield of anhydrous trimethylamine oxide is around 95%. The material is extremely hygroscopic. A sample in a capillary tube melts at 208° after subliming around 180°. 

Ti02 nanopartides [10-12], NiO nanopartides [13] and various nanopartides of metal oxides [14] are formed in droplets or in a micellar environment. Cottam et al. reported a microfluidic synthesis of small nanorods of titanium oxide by fast mixing of an oleic add solution of tetraisopropoxytitanium (TTIP) with trimethylamine N-oxide dihydrate (TMAO) [15]. Both reaction solutions were mixed by a Y-shaped micro channel structure and conducted through a 40 cm microchannel with an internal channel width of 100 Jim. As a result, bunched assemblies of rod-like titanium dioxide were obtained. The length of the bundles was more than 100 nm and the diameter of the single rods was less than 10 nm. 

Kabalka, G. W., Slayden, S. W. 1977. Oxidation of organoboranes with trimethylamine N-oxide dihydrate. J. Organomet. Chem. 125 273-280. 

The dihydrocarbazolone iron complex (49 mg, 0.119 mmol) is dissolved in acetone (2 mL), trimethylamine /V-oxide dihydrate (74 mg, 0.666 mmol) is added, and the reaction mixture is stirred for 4 h at room temperature. The heterogeneous mixture is filtered... 

Oxidation of organoboranes (6, 624 8, 507). A new synthesis of acylsilanes (2) involves oxidation of the hydroboration products of alkynylsilanes (I).1 Oxidation with the commercially available dihydrate of trimethylamine N-oxidc is sluggish however, anhydrous reagent2 is satisfactory for this purpose (equation I). 

Trimethylamine N-oxide, either anhydrous or as its readily available dihydrate, smoothly oxidizes a wide variety of alkyl, cycloalkyl, aryl and heterocyclic boron derivatives to the corresponding oiganyl-oxyboranes (equation 22) which, in Ae case of the dihydrate, are hydrolyzed in the reaction mixture. Anhydrous trimediylamine N-oxide is simply prepared and this reagent must be used for the oxidation of a enylboranes if prior hydrolysis is not to compete with oxidation. > Alkynylboranes are not oxidized by trimethylamine N-oxide. ... 

Caution. Anhydrous trimethylamine-N-oxide is obtained by vacuum sublimation of the commercial dihydrate Aldrich Chemical Company)... 

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