JV-Bromosuccinimide

METHYL y-BROMOCROTONATE JV-Bromosuccinimide. Dissolve, with the aid of rapid mechanical stirring, 80 g. of pure succinimide (Section V,14) in a mixture of 150 g. of finely crushed ice and a solution of 32 g. of sodium hydroxide in 200 ml. of water contained in a litre beaker and cooled externally by ice. Immediately the imide has dissolved, continue the vigorous stirring and introduce 42 -5 ml. of bromine in one lot from a separatory funnel supported over the beaker it is essential that the bromine be instantly suspended in the solution. After stirring vigorously for 2 minutes, filter at the pump and... 

The benzylic position of an alkylbcnzene can be brominated by reaction with jV-bromosuccinimide, and the entire side chain can be degraded to a carboxyl group by oxidation with aqueous KMnCfy Although aromatic rings are less reactive than isolated alkene double bonds, they can be reduced to cyclohexanes by hydrogenation over a platinum or rhodium catalyst. In addition, aryl alkyl ketones are reduced to alkylbenzenes by hydrogenation over a platinum catalyst. 

Bromination of 7-ter/-butyl, 2-mcthyl 5-methyl-4//-azepine-2,7-dicarboxylate (7) with 1 equivalent of jV-bromosuccinimide yields 2-terf-butyl,7-methyl 4-(bromomethylene)-4,5-dihvdro-l//-azepinc-2,7-dicarboxylate (8) as a 1 2 mixture of the E- and Z-isomers.113 With an excess of reagent the dibromomethylene compound 9 results. 

Bromofluorination of double bonds using polymer-supported hydrogen fluoride-jV-bromosuccinimide (NBS) or BU4NF-NBS (Ref. 330) has been reported. 

As with chlorine-containing oxidants, JV-bromo species have been used to oxidize sulphoxides to sulphones (with no bromine incorporation) through the initial formation of a bromosulphonium ion, by nucleophilic attack of the sulphoxide sulphur atom on the electrophilic halogen atom. Such reactions involve JV-bromosuccinimide ° bromamine-T, iV-bromoacetamide ° and iV-bromobenzenesulphonamide. All reported studies were of a kinetic nature and yields were not quoted. In acid solution all oxidations occurred at or around room temperature with the nucleophilic attack on the electrophilic bromine atom being the rate-limiting step. In alkaline solution a catalyst such as osmium tetroxide is required for the reaction to proceed . ... 

Dissolve 71 g. of P-methylnaphthalene in 460 g. (283 ml.) of A.B. carbon tetrachloride and place the solution in a 1 -litre three-necked flask equipped with a mechanical stirrer and reflux condenser. Introduce 89 g. of JV-bromosuccinimide through the third neck, close the latter with a stopper, and reflux the mixture with stirring for 16 hours. Filter ofiT the succinimide and remove the solvent under reduced pressure on a water bath. Dissolve the residual brown oil (largely 2-bromomethyl naphthalene) in 300 ml. of A.R. chloroform, and add it to a rapidly stirred solution of 84 g. of hexamine in 150 ml. of A.R. chloroform contained in a 2-litre three-necked flask, fitted with a reflux condenser, mechanical stirrer and dropping funnel maintain the rate of addition so that the mixture refluxes vigorously. A white solid separates almost immediately. Heat the mixture to reflux for 30 minutes, cool and filter. Wash the crystalline hexaminium bromide with two 100 ml. portions of light petroleum, b.p. 40-60°, and dry the yield of solid, m.p. 175-176°, is 147 g. Reflux the hexaminium salt for 2 hours with 760 ml. of 60 per cent, acetic acid, add 160 ml. of concentrated hydrochloric acid, continue the refluxing for 5 minutes more, and cool. Extract the aldehyde from the solution with ether, evaporate the ether, and recrystallise the residue from hot -hexane. The yield of p-naphthaldehyde, m.p. 69-60°, is 60 g. 

Acyclic ADC compounds, which are more correctly named as derivatives of diazene, are generally prepared from hydrazine derivatives. For example, diethyl azodicarboxylate (Chemical Abstracts name diethyl diazene-1,2-dicarboxylate)5 is prepared from hydrazine by treatment with ethyl chloro-formate followed by oxidation with chlorine in benzene-water.6 Other oxidants which have been used include JV-bromosuccinimide,7 nitric acid,8 inorganic nitrates,9 potassium dichromate,10 silver carbonate on celite,11 and phenyl iodosotrifluoroacetate.12 The hydrazine derivative may also be... 

Br + H2OCHCH3H2C=CHCH,Br + HBr The low concentration of Br comes from jV-bromosuccinimide (NBS). 

Furthermore, 41 % hydrogen fluoride/ polyvinylpyridine combined with jV-bromosuccinimide as coreagent has been used in the preparation of alkyl fluorides from alcohols (Table 18) in good yields. 

Radical-mediated brominations of carbohydrate derivatives have usually been conducted in refluxing carbon tetrachloride, under a tungsten (150— 250 W) or heat (250-450 W) lamp, with either JV-bromosuccinimide (1.2— 5 molar equivalents) or bromine (2-5 equivalents) as the source of halogen. Addition of bromotrichloromethane to the carbon tetrachloride can be advantageous.25 Substrate concentrations have ranged from 0.02 to 0.2 mol.l-1 and have depended to some degree on solubility factors, and ordinary laboratory glassware has most often been used. 

When penta-O-acetyl-a-D-idopyranose (25) was subjected to radical bro-mination using jV-bromosuccinimide as source, it gave, in good yield, penta-0-acetyl-5-bromo-/ -L-glucopyranose (26) (see Scheme 5), which is the en-... 

Reaction of the ribofuranose ester 36 with jV-bromosuccinimide again resulted in C-4 substitution, to give the bromides 37 and 38 in the ratio of 3 2, and compound 35 and close analogs remain the only orthoamides encountered during these studies. 

Very efficient reaction occurs when phenyl 1 -thio-/ -D-glucopyranoside and -D-galactopyranoside tetrabenzoates (94 and 95) are treated in refluxing carbon tetrachloride with JV-bromosuccinimide under a heat lamp, and, within 15 minutes, they are converted into products from which the enones 96 and 97 have been obtained by direct crystallization in 76 and 83% yield, respectively (see Scheme 15).20... 

Selective bromination of monobromo-substituted dithienyl sulfides with JV-bromosuccinimide afforded two more dithienothiophene isomers.124 From the reaction of 3-thienyllithium with disulfide 182 at —70°, 4-bromo-3,3 -dithienyl sulfide (185) was isolated. Bromination with JV-bromosuccinimide provided 2,4 -dibromo-3,3 -dithienyl sulfide (186) dilithiation of the latter followed by oxidative ring closure gave dithienothiophene 9 in 13% overall yield [Eq. (54)]. 

IR spectroscopy has shown that thienothiophenes 1 and 2 are brominated with JV-bromosuccinimide to furnish dibromo along with monobromo derivatives.172 An unpurified bromination product of thienothiophene 1 contained 8% of the initial thienothiophene 1, 83% of 2-bromothieno[2,3-h]thiophene, and 9% of 2,5-dibromothieno[2,3-i]-thiophene 15% of the initial thienothiophene 2, 70% of 2-bromothieno-[3,2-ft]thiophene and 15% of 2,5-dibromothieno[3,2-6]thiophene were detected on bromination of thienothiophene 2.172... 

Bromination by two equivalents of JV-bromosuccinimide in glacial acetic acid gave good yields (65% and 88%) of 2,5-dibromo derivatives of thienothiophenes 1 and 2, and 2,3,5-tribromo derivatives were obtained using three equivalents of bromine in carbon disulfide (75% and 81% yields).172... 

Methyl y-bromocrotonate. Mix 36 g (0.2 mol) of jV-bromosuccinimide, 20 g (0.2 mol) of methyl crotonate and 60 ml of dry, redistilled carbon tetrachloride in a 500-ml round-bottomed flask. Reflux on a water bath for 12 hours by this time all the solid should have risen to the surface of the liquid. Filter off the succinimide at the pump and wash it with a little dry carbon tetrachloride. Remove the solvent on a water bath and distil the residue under reduced pressure through a short fractionating column. Collect the methyl y-bromocrotonate at 77-78 °C/8mmHg the yield is 31 g (86%). 

Benzylidene acetals can be oxidatively cleaved by jV-bromosuccinimide (NBS) to give 6-bromo-4-benzoyl-hexopyranosides (see Chapter 3). This reaction has also been performed on 1,2-0-benzylidene derivatives and it appears that the cleavage reactions result in the formation of a derivative that has an axial benzoyl ester.33... 

When exposed to air, or better to manganese dioxide, 1,2-dihydroisoquinolines are readily oxidized to isocarbostyrils,8,105 whereas with iodine,77 mercuric acetate,78 or jV-bromosuccinimide,106 the products are the fully aromatic isoquinolinium salts. 

Dibenzoyl tellurium and jV-bromosuccinimide combined in refluxing chloroform to yield dibenzoyl tellurium bromide succinimide1. 

The reaction with JV-bromosuccinimide gave only a 45% yield of diphenyl tellurium oxide. 

Side-chain halogenation is illustrated also by the bromination of p-nitrotoluene (Expt 6.28). The radical mechanism with molecular bromine is similar to that of chlorination above JV-bromosuccinimide has also found use as a side-chain brominating reagent and its application is described in Expts 6.119 and 6.152. 

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