Sodium bromite oxidation

Sodium bromite oxidizes secondary alcohols in preference to primary alcohols. Menthol treated with sodium bromite in aqueous acetic acid at room temperature affords an 86% yield of menthone after 5.5 h [739]. 

The most widely used, and often most convenient reagents for such one-pot reactions are sodium hypochlorite (45) or hypobromite (16). These reactions are performed in the presence of an organic base (generally triethylamine) that normally enhances the yield of cycloaddition products (45). This method was employed for many intermolecular reactions (71) and also seems especially suited for intramolecular ones (72-77) as well as for the solid-phase synthesis (78) of 2-isoxazolines. Hypohalite can also be replaced by sodium bromite in combination with a catalytic amount of tri-n-butyltin chloride (79). In a related method, O-tributylstannyl oximes were treated with fert-butyl hypochlorite to produce nitrile oxides that were trapped with alkenes or alkynes to afford the corresponding isoxazolines or isoxazoles in moderate to good yield (80). 

Apart from sodium hypochlorite, a number of alternative secondary oxidants for TEMPO-mediated alcohol oxidations can be employed. These include cerium (IV) ammonium nitrate (CAN),24 trichloroisocyanuric acid (TCCA),25 oxone ,26 MCPBA,2,3,7 PhI(OAc)2,27 W-chlorosuccinimide,28 sodium bromite,29 electrooxidation,8,21 H5IO626 and a polymer-attached diacetoxybromide (I) complex.30... 

Both, sodium bromite (NaBr02)51 and sodium bromate (NaBr03)52 are able to carry out selective oxidations of secondary alcohols in the absence of an added catalyst under properly devised experimental conditions. 

Sodium bromite (NaBr02) is a relatively new reagent in this group. Its main application is in oxidations, but it has also been used for the direct conversion of olefins into p-bromo ketones831. 

Ammonium cerium(IV) nitrate or cerium(IV) sulfate will catalyze the selective oxidation of secondaiy alcohols with sodium bromate as cooxidant, in this case remote C—C double bonds interfere, but 1,2-diols are not cleaved. It has been found that sodium bromite in aqueous acetic acid will act as a selective oxidant for secondary mary diols without the need for other catalysts (Scheme 21). ... 

Sodium bromite, NaBr02 H20, a crystalline compound, oxidizes secondary alcohols to ketones [739] and sulfides to sulfoxides [739]. Primary alcohols are transformed into esters [739]. 

There are a variety of stoichiometric oxidants that can be used in conjunction with 2,2,6,6-tetramethylpiperdine 1-oxyl (TEMPO), including TCCA, iodobenzene diacetate, meto-chloroperbenzoic acid (wi-CPBA), sodium bromite, sodium hypochlorite, and /V-chloi osuccinirnide. TEMPO can be used to oxidize primary alcohols to aldehydes or carboxylic acids, based on reaction conditions. A particularly attractive feature is that the product is usually isolated quite pure after concentration of the organic layer. 

Cycloalkenes and styrenes have been epoxidized by an aqueous solution of sodium bromite in the presence of CuS04 5H20 at room temperature [14]. In the absence of copper ion, no epoxidation occurs. It has been hypothesized that the unstable Cu(Br02)2 is the oxidizing species (Scheme 6.2). Manganese porphyrin complexes have been used to catalyze the epoxidation of simple alkenes in aqueous medium. 

In opocinchenine the hydroxyl group must, therefore, be in the ortho-position relative to the point of attachment of the benzene ring to the quinoline nucleus. The relative positions of the two ethyl groups are determined by the fact that apocincheninic acid ethyl ether on oxidation with lead peroxide and sulphuric acid gives the lactone of hydroxyopo-cincheninic acid ethyl ether (I), which, on oxidation by sodium hypo-bromite, yields quinolylphenetoledicarboxylic acid (II). 

The traditional method of oxidizing hydrazine derivatives makes use of halogens or hypohalites as oxidizing agents. The techniques range from the preparation of l,l -azobis(l-cyclohexanenitrile) by the addition of bromine to an alcoholic hydrochloric acid solution of the corresponding hydrazine [89], through the use of bromine water [90, 91] to oxidations with sodium hypo-bromite [64] or sodium hypochlorite [92]. 

Other oxidizing agents such as bichromate, iodate, bromate, chlorite, bromite, chloramine T, and peroxosulfate are not equally suitable for all dyes and are seldom used, for price reasons or because of contamination of the wastewater with heavy metals. Sodium hypochlorite requires careful metering and can be used only with sulfur dyes that are relatively fast to chlorine. 

Hydrastine has been prepared by the hydrogenolysis of the 1-phenyl-l/f-5-tetrazolyl ether of (—)-a-narcotoline,154 and in the racemic form by the reductive cyclization of the quaternary salt of the keto-acid (53) that is obtained from oxidoberberine (51) as described above.133 The lactone (80), prepared by the dye-sensitized photo-oxidation of oxidonorcoralyne followed by reduction with sodium borohydride and from 6 -acetylpapaveraldine by oxidation with hypo-bromite followed by reduction, has been TV-methylated and reduced with sodium borohydride to an isomer of cordrastine.133 Cordrastine itself has been synthesized by the electrolytic reduction of a mixture of the iminium salt (81) and bromomeconine (82), a process that has been shown to be of general applicability to the synthesis of alkaloids of this group.155... 

Most of mixtures of oxidizer and red phosphorus possess very high sensitivity. The results of drop hammer tests for this kind of mixture is shown in Sec.3.3. In the range of experiments, the mixtures of red phosphorus with bromite, chlorite and sodium peroxide possess very high sensitivity. 

Methylsuccinic acid has been prepared by the pyrolysis of tartaric acid from 1,2-dibromopropane or aHyl halides by the action of potassium cyanide followed by hydrolysis by reduction of itaconic, citraconic, and mesaconic acids by hydrolysis of ketovalerolactonecarboxylic acid by decarboxylation of 1,1,2-propanetricarboxylic acid by oxidation of /S-methylcyclo-hexanone by fusion of gamboge with alkali by hydrog nation and condensation of sodium lactate over nickel oxide from acetoacetic ester by successive alkylation with a methyl halide and a monohaloacetic ester by hydrolysis of a-methyl-a -oxalosucdnic ester or a-methyl-a -acetosuccinic ester by action of hot, concentrated potassium hydroxide upon methyl-sucdnaldehyde dioxime from the ammonium salt of a-methyl-butyric add by oxidation with. hydrogen peroxide from P-methyllevulinic add by oxidation with dilute nitric acid or h3 bromite from 8-methyladipic acid and from the decomposition products of glyceric add and pyruvic add. The method described above is a modification of that of Higginbotham and Lapworth. ... 

Small amounts of oxygen gas may be made from small amounts of Oi -enriched water (25 to 200 mg.) by the procedure described by Anbar (1958) for the isotopic analysis of oxygen in water. Sodium hypo-bromite is formed in situ from aqueous sodium hydroxide and bromine in a sealed tube, and, in the presence of a trace of cobaltic oxide, the hypo-bromite decomposes with the evolution of oxygen. The sealed tube is then broken open on a vacuum line. The oxygen is drawn off and the water recovered by distillation. 

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