N -Bromosuccinimide

Three molar equivalents of bromine is added with cooling to a mixture of 1 molar equivalent of quinoline and 3 gram-atom equivalents of sulfur, and the resulting mixture is heated to 180-200° in an oil bath for 2 hours. The cooled reaction mass is extracted several times with hot concentrated hydrochloric acid, and the combined extracts are made alkaline with sodium hydroxide. Ether extraction of the alkaline mixture followed by distillation of the ethereal solution gives a 50% yield of 3-bromoquinoline boiling at 158—162°/24 mm. 

Succinimide (160 g., 1.62 moles) is dissolved in an externally cooled mixture of 64 g. (1.60 moles) of sodium hydroxide, 300 g. of crushed ice, and 400 ml. of water. Bromine (85 ml.) is added all at once to the vigorously stirred reaction mixture. Stirring is continued for 1-2 minutes, after which the precipitate is collected by filtration. The filter cake is washed with ice-cold water until the washings are free 

A solution of 16 ml. (47 g., 0.29 mole) of bromine in 250 ml. of glacial acetic acid is added at 10° to a solution of 25 g. (0.30 mole) of thiophene in 125 ml. of acetic acid. The oil precipitated by adding excess water to the reaction mixture is taken up in ether. Potassium carbonate is added to the ether for removal of acetic acid. After drying the ethereal solution is distilled and 27 g. (55%) of 2-bromo-thiophene is obtained which boils at 42-46°/13 mm. 

Halogenation of indoles has been performed with a great variety of halogenating agents, which include, in addition to halogens, dioxan dibromide, pyridinium bromide perbromide, N-bromosuccinimide, N-iodosuccinimide, ICl, chloramine T-KI, hypochlorite and /-butyl hypochlorite 394). 

The chemistry of the NBS reaction with indoles has been extensively investigated. It seems relevant to discuss this here together with some aspects related to the bromination of tryptophan and related 3-substi-tuted indoles 175, 218, 295, 443). 

NBS reacts with the indole nucleus following the normal pattern of electrophilic substitution attack at the 3-position is favored. When this position is blocked substitution occurs at the 2-position. Indole and 3-alkylated indoles exposed to one mole of NBS under anhydrous conditions yield 3-bromoindole and 2-bromo-3-alkylindoles respectively 175,394). By contrast, halogenation in hydroxylic solvents often leads directly to oxindoles and both 2- and 3-halo-indoles readily form 

3- substituted indoles with NBS in /-butyl alcohol. When 1 1 molar ratios of indole and brominating agent are used and this is followed by treatment with water, yields up to 50% of the corresponding oxindole can be obtained. Use of a second mole of NBS results in the formation of 3-bromooxindoles. On the other hand, when the NBS reaction was performed in aqueous media, 5-bromooxindole was formed. Subsequent bromination in the 5-position is apparently greatly retarded in /-butyl alcohol relative to water. 

The reaction of 3-methylindoles with NBS in pyridine at room temperature results in a quantitative yield of the pyridinium salt (91), which by acid hydrolysis is converted to 3-methyloxindole (92), 77, 226). 

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The addition of N-bromosuccinimide (1.1equiv) to a dichlo-romethane solution containing the alkene (1 equiv) and cyana-mide (4 equiv). The solution was maintained at room temperature (3 days) and then washed with water, dried, and concentrated in vacuo. Treatment of the bromocyanamide [intermediate] with 1% palladium on charcoal in methanol (1h) led to reduction of the for-madine. Addition of base to the reaction mixture (50% aqueous KOH, reflux 6h) followed by extraction with ether gave monoamine. (Yield is 48-64% final amine from alkenes analogous to safrole)... 

Bromination has been described using brominating agents such as N-bromosuccinimide in carbon tetrachloride (418. 420) bromine in either chloroform, acetic acid, or hydrochloric acid (414. 418, 421-423) bromine in sulfuric acid (415-417) and enzymatic catalysis (424, 425). 

The bromination with N-bromOsuccinimide in CCU can be accomplished yielding to 2-brOmothiazole (12.5% yield) (27). 

Halogenation (Section 11 12) Free radical halo genation of alkylbenzenes is highly selective for substitution at the benzylic position In the exam pie shown elemental bromine was used Alterna Lively N bromosuccinimide is a convenient re agent for benzylic bromination... 

A certain compound A when treated with N bromosuccinimide and benzoyl peroxide under photochemical conditions in refluxing carbon tetrachloride gave 3 4 5 tnbromobenzyl bromide in excellent yield Deduce the structure of compound A... 

The content of ascorbic acid, in milligrams per 100 mL, in orange juice is determined by a redox titration using either 2,6-dichlorophenolindephenol or N-bromosuccinimide as the titrant. 

The iacreased chemical stabiUty of the 6-deoxytetracyclines allows chemical modification with retention of biological activity electrophilic substitutions have been carried out at C-7 and C-9 under strongly acidic conditions (46—53). Reactions of 6-deoxy-6-demethyltetracycline [808-26-4] (16), C21H22N2O7, with electrophiles, such as nitrate ion (49), bromomium ion (46,47) (from N-bromosuccinimide), or N-hydroxymethylphthalimide (53), yielded 7-substituted tetracyclines. In the case of the nitration reaction, both the 7- and 9-nitro isomers (17, X = NO2, Y = H) and (17, X = H, Y = NO2) were obtained. 

Allylicor benzylic bromination or chlonnalion with N bromosuccinimide (NBS) or NCS... 

NCS A-chlorosuccmimidc NBS, N bromosuccinimide, NBA, A-bromo-acetamidc NIS W-iodosuccinimide RT room tempcraaire TMS tetramethylenesulfone... 

Formyl- and 4-bromo-3-formyl-isothiazole have been prepared in good yield from the dibromomethyl compounds obtained by side-chain halogenation of the appropriate 3-methylisothiazole with N-bromosuccinimide. 3-Acetyl- and 3-acetyl-4-bromo-isothiazole have been prepared from the 3-cyanoisothiazoles and methyl magnesium iodide. ... 

The isoxazole nucleus is also halogenated in the 4-position by N-bromosuccinimide provided there is no substituent in this position. This reaction does not proceed homolytically, as might have been expected, and appears to represent a simple electrophilic substitution by the bromine cation. Similar cases have been previously described for the bromination of certain aromatic compounds with A -bromo-succinimide. ... 

Olefins react with bromine by addition of the latter to the carbon-carbon double bond. In contrast the Wohl-Ziegler bromination reaction using N-bromosuccinimide (NBS) permits the selective substitution of an allylic hydrogen of an olefinic substrate 1 by a bromine atom to yield an allylic bromide 2. 

The allylic bromination of an olefin with NBS proceeds by a free-radical chain mechanism. The chain reaction initiated by thermal decomposition of a free-radical initiator substance that is added to the reaction mixture in small amounts. The decomposing free-radical initiator generates reactive bromine radicals by reaction with the N-bromosuccinimide. A bromine radical abstracts an allylic hydrogen atom from the olefinic subsfrate to give hydrogen bromide and an allylic radical 3 ... 

In order to induce the free-radical chain reaction, a starter compound such as dibenzoyl diperoxide, azo-Zj -(isobutyronitrile) or tcrt-butyl hydroperoxide or UV-light is used. The commercially available, technical grade N-bromosuccinimide contains traces of bromine, and therefore is of slight red-brown color. Since a small amount of elemental bromine is necessary for the radical... 

One such compound, bropirimine (112), is described as an agent which has both antineo-plastic and antiviral activity. The first step in the preparation involves formation of the dianion 108 from the half ester of malonic acid by treatment with butyllithium. Acylation of the anion with benzoyl chloride proceeds at the more nucleophilic carbon anion to give 109. This tricarbonyl compound decarboxylates on acidification to give the beta ketoester 110. Condensation with guanidine leads to the pyrimidone 111. Bromination with N-bromosuccinimide gives bropirimine (112) [24]. 

Dihydroxy-16 methyl-4,9(11 )-pregnadiene-3,20-dlone 21 Acetate N-Bromosuccinimide Perchloric Acid... 

Preparation of 9a-Bromo-110,17a 1 Trihydroxy-16 -Methyl-4-Pregnene-3,20-Dione 21-Acetate To a mixture of 620 mg of 17a,21-dihydroxy-16/3-methyl-4,9(11 )-pregnadiene-3,20-dione 21-acetate and 330 mg of N-bromosuccinimide in 10 ml of dioxane and 3.2 ml of water cooled to 10°C was added 1.8 ml of cold 1 M aqueous perchloric acid. The mixture was stirred at 15°C for 3 hours. Excess N-bromosuccinimide was destroyed by addition... 

A solution of 3.4 grams of N-bromosuccinimide in 60 cc of absolute dioxane is added drop wise in the dark, during the course of 5 minutes, to a stirred solution, heated to 60°C, of 9.2 grams of ergocryptine in 180 cc of absolute dioxane. The reaction mixture is stirred at this temperature for 70 minutes and is concentrated to a syrup-like consistency in a rotary evaporator at a bath temperature of 50°C. The reaction mixture is subsequently diluted with 300 cc of methylene chloride, is covered with a layer of about 200 cc of a 2N sodium carbonate solution in a separating funnel and is shaken thoroughly. The aqueous phase is extracted thrice with 100 cc amounts of methylene chloride. The combined... 

Acetoxy-5a-Hydroxy-17a-Methy/-17 -Carbomethoxyandrostane-6-one itttb) 3(3,5o ,6(3-Trihydroxy-17a-methyl-17(3-carbomethoxyandrostane (II, 5.2 g) is dissolved In methanol (105 ml) to which ether (105 ml) and water (84 ml) are added. Then N-bromosuccinimide (5.2 g) is added with stirring and the clear solution is left in the refrigerator for 3 hours. The ether is removed under reduced pressure at room temperature and a crystalline solid (Ilia) separates,... 

Bromo pyruvaldoxime Methotrexate N-Bromosuccinimide Betamethasone acetate Bromocriptine Medrogestone 2-Bromothiophene Thihexinol... 

Cyclization of /V-carbethoxyhydrazone 57 and ALformylhydrazone 58 of pyrrole-2-carbaldehyde gave 59 (73CC35 80JHC631) by base-catalyzed cyclodehydration. The expected substitution product at 6-position was obtained from the reaction of 58 with N-bromosuccinimide (Scheme 15). 

Aqueous solutions of aequorin also emit light upon the addition of various thiol-modification reagents, such as p-quinone, Br2, I2, N-bromosuccinimide, N-ethylmaleimide, iodoacetic acid, and p-hydroxymercuribenzoate (Shimomura et al., 1974b). The luminescence is weak and long-lasting ( 1 hour). The quantum yield varies with the conditions, but seldom exceeds 0.02 at 23-25°C. The luminescence is presumably due to destabilization of the functional moiety caused by the modification of thiol and other groups on the aequorin molecule. 

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