Af-Bromosuccinimide

Aryl and alkylxanthates are converted into difluoro(methylthw)methyl ethers with tetrabutylammonium dihydrogen trifluoride and Af-bromosuccinimide in... 

Trimethylsilyl halides can also be used for analogous reactions with arenediazo-nium tetrafluoroborates, as shown by Keumi et al. (1989). These authors treated 2-fluorenediazonium tetrafluoroborate in A/,Af-dimethylformamide or -acetamide with trimethylsilylchloride, -bromide, or -iodide in the presence of an excess of N-chlorosuccinimide, Af-bromosuccinimide, or methyl iodide, respectively, at 60 °C (Cl, Br) or at room temperature (I). The yields of the 2-halofluorenes were good in addition fluorene, the product of hydro-de-diazoniation, was obtained, if the reaction was run in tetrahydrofuran/Af,7V-dimethylformamide mixtures. The mechanism of these reactions, as well as that of the corresponding azido-de-diazoniation, is uncertain (see also Secs. 10.2 and 10.7). 

By treatment of (Z)-2-chlorovinyltellurium trichlorides, easily obtained by addition of tellurium tetrachloride to phenylacetylenes (see Section 3.16.2.1), with 1-2 mol equiv of iodine or Af-bromosuccinimide-aluminium trichloride, a halogenodetelluration occurs, generating the corresponding (Z)-iodo- or (Z)-bromochloroalkenes. °... 

Some unusual electrophiles are shown. Benzothiazines 219-221 were reacted with HNO2 to give the versatile A -nitroso derivatives 222-224 or with cyclopentenone/Af-bromosuccinimide (NBS) to give 225-227 (Scheme 24) <2003JME3670>. Dihydrothiazinedicarboxylic acid 228 was reacted with 2,2-dimethoxypropane to form bicyclic product 229 (Equation 18) <1968T2985>. 

In this same study, the authors also reported isolation of oxazoline 90 in moderate yield when propenylbenzamide 88 was reacted with Af-bromosuccinimide (NBS) in CCI4. A radical mechanism via intermediates 89a and 89b has been proposed. The generality and scope of this method has not been established (Scheme 8.30). 

Treatment of a carborane derivative of thiirane with Af-bromosuccinimide gives a j8-bromodisulfide (79MI50601). Chlorination of cz s-2,3-di-r-butylthiirane by f-butyl hypochlorite proceeded differently to the reaction with chlorine itself (Scheme 41) (74JA3146). 

Af-bromosuccinimide [128-08-5] C4H4BrN02 180-183 2.098 brominating olefins, oxidizing alcohols to aldehydes and ketones, converting aldehydes to acid bromides 151,152... 

To a solution of phenylthio disaccharide 3 (56 mg, 0.11 mmol) in CHjC (2 mL) at —15°C was added DAST (21 pL, 0.16 mmol), followed by Af-bromosuccinimide (25 mg, 0.14 mmol). After stirring at — 15°C for 15 min, the reaction mixture was poured onto saturated aqueous NaHC03 solution (5 mL) and extracted with ether (3 x 10 mL). The organic extracts were combined, washed with brine (5 mL), and dried (MgS04). Evaporation of the solvent followed by flash chromatography (silica, ether-petroleum ether) gave the disaccharide fluoride 4 (40 mg, 85%) with an anomeric ratio of 5 1 (oc/p). 

To a solution of 86 (1.25 g, 1.65 mmol) in dry acetonitrile (30 mL) were added the aspartic acid derivative 87 (652 mg, 1.83 mmol) and AF-bromosuccinimide (444 mg, 2.50 mmol). The mixture was stirred in the dark at room temperature under argon. After 1 h, aqueous NajSjOj (10 mL) was added, the bulk of organic solvent was evaporated under reduced pressure, and the residue was partitioned between water (100 mL) and chloroform (100 mL). The aqueous layer was extracted with chloroform (3 x 100 mL). The combined organic layers were washed with water (2 x 75 mL) and dried, and the solvent was removed under reduced pressure. Flash column chromatography (light petroleum-ethyl acetate, 4 1)... 

Treatment of pyrrole, 1-methyl-, 1-benzyl- and 1-phenyl-pyrrole with one mole of Af-bromosuccinimide in THF results in the regiospecific formation of 2-bromopyrroles. Chlorination with jV-chlorosuccinimide is less selective (81JOC2221). Bromination of pyrrole with bromine in acetic acid gives 2,3,4,5-tetrabromopyrrole and iodination with iodine in aqueous potassium iodide yields the corresponding tetraiodo compound. 

Alkenes react with Af-bromosuccinimide (NBS) to give allylic bromides. NBS serves as a source of Br2, and substitution occurs by a free-radical mechanism. The reaction is used for synthetic purposes only when the two resonance forms of the allylic radical are equivalent. Otherwise a mixture of isomeric allylic bromides is produced. 

General Procedure for Selective Oxidation of Secondary Alcohols in Presence of Primary Alcohols by Treatment of Intermediate Tin Alkoxides with Bromine or Af-Bromosuccinimide... 

A typical procedure is that described in Expt 6.119 for the synthesis of 1-naphthaldehyde. The synthesis of p-nitrobenzaldehyde provides an example in which the intermediate crystalline hexamine salt is isolated prior to hydrolysis. 2-Naphthaldehyde is prepared from the bromomethyl compound, the preparation of which illustrates the use of Af-bromosuccinimide for effecting benzylic bromination of 2-methylnaphthalene. 

The formation of oxygen- and carbon-centered radicals by the thermolysis of peroxides or azo compounds is well known. Today, these compounds have been also used as radical initiators. For example, treatment of a CC14 solution of toluene and Af-bromosuccinimide (NBS) in the presence of a catalytic amount of benzoyl peroxide in refluxing conditions gives benzyl bromide in good yield as shown in Scheme 1.5. This is called the Wohl-Ziegler reaction. 

The bromofluorination of methylcnecyclohexanes can be carried out with Af-bromosuccinimide and triethylaminc/hydrogen fluoride 158 for example, the formation of 1 from l-methyl-2-methylcnecyclohexane. 

Substituted aryl hydrazones can be converted to geminal difluorides in satis factory yields by molecular fluonne [S4, iodine fluoride [ 5], and N bromo-suc-cimmide-pyridinium polyhydrogen fluoride or Af-bromosuccinimide-polyvi-nylpyridinium polyhvdrogen fluoride [56] (equation 21) (Table 6)... 

Beside the Grignard and other C-C bond-forming reactions, a number of functional group transformations may also serve as an entry into allylic systems. Some of them, namely the reduction of a, -unsaturated carbonyl compounds (products of crotonic condensation), halogenation of alkenes at the allylic position with Af-bromosuccinimide (NBS) and epoxide isomerization, are shown in Scheme 2.56. 

Using 5,7-dimethyl-[l,2,3]triazolo[l,5-fl]pyrimidine (214), Af-bromosuccinimide in chloroform yielded not the expected 3-bromo product (215), but 2-(a,a-dibromomethyl)-4,6-dimethylpyrimidine (216) and, in lesser amounts, 4,6-dimethylpyrimidine-2-carbal-dehyde diethyl acetal (217) (76JOC385). The latter product was due to ethanolysis of (216) by the trace amounts of ethanol in the solvent since, following its removal, (216) was the only product. Use of iV-chlorosuccinimide and iodine monochloride proceeded in the same way giving rise to (218) and (219), respectively. The mechanism for these transformations is illustrated in Scheme 12 and is postulated to involve a diazonium cation (76JOC385). 

Fig. 5. Ultraviolet spectra of Cbz-Try with Af-bromosuccinimide in aqueous acetate buffer of pH 4,0. A. Recorded directly. B. Recorded as difference. From Patch-ornik et al. (1960).

Fig. 9. Effect of pH on rate of consumption of Af-bromosuccinimide (0.04 M) by leucine (0.01 M), From Schmir and Cohen (1961).

Predict the product of the reaction of p-methylbenzoic acid with each of the following (a) BH3, then H jO tb) Af-Bromosuccinimide in CCI4... 

The e do-adduct 21 from methoxycarbonylcarbene and cyclohexa-1,3-diene on treatment with Af-bromosuccinimide gave a mixture of thermolabile bromides which rearranged under the reaction conditions to produce methyl cyclohepta-2,4,6-trienecarboxylate (22). ... 

Electrophilic substitutions of 3-hydroxypyridine take place at C-2, for example nitration, Mannich substitution and iodination. " Its phenol-like character is nicely illustrated by efhcient 2,4,6-tribromination with Af-bromosuccinimide. 2-Methoxypyridine brominates at C-5 and 4-methoxypyridine at C-3. ... 

Monoiodination of 2-substitnted thiophenes, whether the substituent is activating or deactivating, proceeds efficiently at the remaining a-position using iodine with iodobenzene diacetate. 3-Alkyl-thiophenes can be monobrominated or monoiodinated at C-2 using Af-bromosuccinimide, or iodine with mercury(II) oxide, respectively. 

Af-Bromosuccinimide has also been used for the bromination of furan derivatives e.g., 2-furoic ester is converted into the 5-bromo derivative (15% yield) but furan itself resiniiies. 

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