N-Bromosuccinimide oxidant

A few reagents have been reported for the allylic oxidation of particular substrates. These include N bromosuccinimide oxidation of a-amyrin acetate in moist dioxane (equation 53), a method later modified by Thomson. 

N-Bromosuccinimide oxidizes the tryptophan side chain and also tyrosine, histidine and cysteine ... 

Epoxyfarnesol was first prepared by van Tamelen, Stomi, Hessler, and Schwartz 4 using essentially this procedure. It is based on the findings of van Tamelen and Curphey5 that N-bromosuccinimide in a polar solvent was a considerably more selective oxidant than others they tried. This method has been applied to produce terminally epoxidized mono-, sesqui-, di-, and triterpene systems for biosynthetic studies and bioorganic synthesis.6 It has also been applied successfully in a simple synthesis of tritium-labeled squalene [2,6,10,14,18,22-Tetracosahexaene, 2,6,10,15,19,23-hexamethyl-, (all-E)-] and squalene-2,3-oxide [Oxirane, 2,2-dimethyl-3-(3,7,12,16,20-pentamethyl-3,7,ll,-15,19-heneicosapentaenyl)-, (all-E)-],7 and in the synthesis of Cecropia juvenile hormone.8... 

It is assumed that the hydrogen bromide released on the oxidation of thiophosphoric acid insecticides with N-bromosuccinimide or bromine vapors forms intensely fluorescent salt-like derivatives with 3-hydroxyflavones — such as robinetin [1, 2, 4]. 

N-Bromosuccinimide purchased from Arapahoe Chemical Company was used without purification. If the purity of the N-bromosuccinimide is in doubt, it should be titrated before use by the standard iodide-thiosulfate method and purified, if necessary, by recrystallization from 10 times its weight of water. Solutions of N-bromosuccinimide in dimethyl sulfoxide cannot be stored, since the solvent is oxidized by the brominating reagent. 

Xb was utilized in the elaboration of the hydrindan XIII and subsequently compound XIV. We expected that Xa could be converted to XIII in the same manner as was in the Sih synthesis. This was confirmed in practice (Scheme II). Oxidation of 569 mg (2.68 mmol) of Xa with pyridinium chlorochromate in methylene chloride furnished 532 mg (94%) of enone Ila (7,21). Treatment of 130 mg of Xa witlj a slight excess of Jones reagent (3,22) afforded 126 mg (98%) of Ila. Allylic brominatlon of Ila with a 20% excess of N-bromosuccinimide (NBS) in refluxing carbon tetrachloride provided Xlla in 98% yield. 

Verdet and Stille1 employed brominated poly(phenylene oxide) intermediates in an effort to synthesize more stable catalyst supports containing (cyclopentadienyl)metal complexes. Treatment of poly(oxy-2,6-dimethyl-l,4-phenylene) with N-bromosuccinimide under photolytic conditions produced only the bromomethyl derivative if the D.F. did not exceed 0.35. Subsequent treatment of the bromomethylated polymer with sodium cyclopentadienide afforded the cyclopentadienyl functionalized polymer, 5, but the reaction was accompanied by crosslinking and it was not possible to remove the bromomethyl substituents quantitatively. 

Hofmann degradation of the nonnatural protoberberine 454 afforded the 10-membered ring base 455 (65%) in addition to the styrene-type compound (13%) (Scheme 92). Dihydroxylation of the former with N-bromosuccinimide in the presence of a large excess of hydrochloric acid and subsequent oxidation of the product diol 456 with periodic acid afforded the dialdehyde 457. On irradiation in tert-butyl alcohol 457 provided ( )-cis-alpinigenine (445) along with ( )-alpinigenine (441) as a result of endo and exo intramolecular cycloaddition, respectively, of the intermediate photodienol (221,222). 

Treating glycosyl isothiocyanates 415 with 5,6-diamino-1,3-dimethyl-uracil (416) gave thioureas 417, which on oxidative cyclization with N-bromosuccinimide afforded 5,7-dioxopyrimido[5,4- ][1,2,4]triazine nucleosides 418 (80MI1 82MI2). 

Formyl C-glycosides, prepared in three steps via the thiazole-based formy-lation of sugar lactones are readily condensed with hydroxylamine to give the corresponding oximes. The latter are the precursors of glycosyl nitrile oxides via the N-bromosuccinimide method (41). 

Residual N-bromosuccinimide from the manufacturing process may be identified and/or quantified by making use of its oxidation potential by titration of liberated iodine after addition of potassium iodide in acetic acid (25). 

N-bromosuccinimide is a selective oxidising agent and oxidises OH groups without disturbing other oxidisable groups. Thus while it does not oxidise aliphatic primary alcohols in presence of water it is highly selective for the oxidation of secondary alcohols to ketones. 

Dihydro-l,2,4-oxadiazoles with hydrogen atoms in the 4- and 5-positions are readily oxidized to 1,2,4-oxadiazoles with air or potassium permanganate <87JHClOl>, chlorine <75JOC248l>, or N-bromosuccinimide <86MI 404-02>. This has been used, for example, for the preparation of oxadiazoles substituted with a carbohydrate moiety (Scheme 71) <86MI 404-02). 

We wish to report here on a new and highly efficient catalyst composition for the aerobic oxidation of alcohols to carbonyl derivatives (Scheme 1). The catalyst system is based on 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO), Mg(N03)2 (MNT) and N-Bromosuccinimide (NBS), utilizes ecologically friendly solvents and does not require any transition metal co-catalyst. It has been shown, that the described process represents a highly effective catalytic oxidation protocol that can easily and safely be scaled up and transferred to technical scale. 

Our initial work on the TEMPO / Mg(N03)2 / NBS system was inspired by the work reported by Yamaguchi and Mizuno (20) on the aerobic oxidation of the alcohols over aluminum supported ruthenium catalyst and by our own work on a highly efficient TEMP0-[Fe(N03)2/ bipyridine] / KBr system, reported earlier (22). On the basis of these two systems, we reasoned that a supported ruthenium catalyst combined with either TEMPO alone or promoted by some less elaborate nitrate and bromide source would produce a more powerful and partially recyclable catalyst composition. The initial screening was done using hexan-l-ol as a model substrate with MeO-TEMPO as a catalyst (T.lmol %) and 5%Ru/C as a co-catalyst (0.3 mol% Ru) in acetic acid solvent. As shown in Table 1, the binary composition under the standard test conditions did not show any activity (entry 1). When either N-bromosuccinimide (NBS) or Mg(N03)2 (MNT) was added, a moderate increase in the rate of oxidation was seen especially with the addition of MNT (entries 2 and 3). 

Tropolone has been made from 1,2-cycloheptanedione by bromination and reduction, and by reaction with N-bromosuccinimide from cyclo-heptanone by bromination, hydrolysis, and reduction from diethyl pimelate by acyloin condensation and bromination from cyclo-heptatriene by permanganate oxidation from 3,5-dihydroxybenzoic acid by a multistep synthesis from 2,3-dimethoxybenzoic acid by a multistep synthesis from tropone by chlorination and hydrolysis, by amination with hydrazine and hydrolysis, or by photooxidation followed by reduction with thiourea from cyclopentadiene and tetra-fluoroethylene and from cyclopentadiene and dichloroketene. - The present procedure, based on the last method, is relatively simple and uses inexpensive starting materials. Step A exemplifies the 2 + 2 cycloaddition of dichloroketene to an olefin, " and the specific oycloadduot obtained has proved to be a useful intermediate in other syntheses. " Step B has been the subject of several mechanistic studies, " and its yield has been greatly improved by the isolation technique described above. This synthesis has also been extended to the preparation of various tropolone derivatives. - " ... 

Acyclic sugar hydrazones react with benzenediazonium chloride to give red formazans. When oxidized with N-bromosuccinimide (or, after acetylation, with lead tetraacetate), these yield tetrazolium salts. 

The isomerization of allyl ethers to 1-propenyl ethers, which is usually performed with potassium tert-butoxide in dimethyl sulfoxide, can also be carried out under milder conditions using tris(triphen-ylphosphine)rhodium chloride,208 and by an ene reaction with diethyl azodicarboxylate,209,210 which affords a vinyl ether adduct. Removal of an O-allyl group may be achieved by oxidation with selenium dioxide in acetic acid,211 and by treatment with N-bromosuccinimide, followed by an aqueous base.201,212... 

Oxidative cyclization of 3-aryl-4-oxo-2-thioxo-tetrahydroquinazolines (278) with N-bromosuccinimide and sulfuric acid gave examples of the title compounds (e.g. 279) (87H2371, 87BSB797). Cyclocondensation of 2-thioxoquinazolines (280) with 2-chlorocyclohexanone (72IJC605) or 4-chloro-3,5-dinitrobenzotrifluoride (87AP569) also afforded benzothia-zolo[2,3- ]quinazolines (e.g. 281). 

The diol (1 mmol) was refluxed with dibutyltin oxide (1 Eq) for 12 h in toluene (20 mL) in an apparatus for the continuous removal of water. The toluene was removed on a vacuum line at 20°C, and the residue was dried for 30 min under reduced pressure (0.1 ton). The residue was taken up in dry chloroform (10 mL), and N-bromosuccinimide (NBS 1 Eq) was added. The stirred reaction mixture was monitorec by TLC. The reaction was complete at times ranging from 2 to 30 min. The mixture was poured directly onto a column for separation using die eluant listed for each compound. 

Phenylselenol, diphenylphosphine and diphenylarsine cleave Pt—Me bonds, but N-bromosuccinimide and 2-nitrobenzenesulfenyl chloride oxidize the methyl platinum(II) compounds to methyl platinum(IV) complexes (equations 208 and 209).573 m-Chloroperbenzoic acid cleaves the Pt—benzyl bond in PtCl(CHDPh)(PPh3)2 with retention of configuration at carbon.574... 

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