W-Bromosuccinimide

The reaction of W-bromosuccinimide with the following compounds has been reported in the chemical literature. Each compound yields a single product in 95% yield. Identify the product formed from each starting material. 

The fully unsaturated tricyclic compounds are also used clinically as antidepressants. Carbamazepine (62), for example, is prepared from 10,ll-dihydro-5H-dibenz[b,f]azepine (49) by N-acetylation followed by bromination with W-bromosuccinimide to give 60. Dehydrohalogenation by heating in collidine introduces the double bond. Saponification with potassium hydroxide in ethanol leads to dibenz[b,f]azepine (61), the parent substance for the fully unsaturated analogs. Treatment of the secondary... 

Procedures for enantioselective synthesis of derivatives of a-bromoacids based on reaction of compounds A and B with W-bromosuccinimide have been developed. Predict the absolute configuration at the halogenated carbon in each product. Explain the basis of your prediction. 

The generation of hydroxy ketones by the brominolysis of stannylenes has been used several times in total synthesis. Experiment G [see Eq. (15)] describes a key step in the total synthesis of the antibiotic (+)-spectinomycin [12,13]. It is remarkable that the two oxygen atoms bound to the tin atom originate from hydroxyl groups, which are port of different functions, a hemiketal and a secondary alcohol. The oxidation is selective for one alcoholic function ont of three. The same product was obtained by W-bromosuccinimide oxidation of the tributylstarmyl ether. 

W-Bromosuccinimide will be seen again as a reagent for selective bromination in Section 11.12. 

Exercise 14-3 The reaction of W-bromosuccinimide (NBS) with alkenes to produce allylic bromides is thought to involve molecular bromine produced by the reaction... 

Radical-chain reaction (Sections 4-4 and 4-5) Br2 is more selective than Cl2 used for preparation of 2-propenyl and arylmethyl halides other reagents include S02CI2 (Section 4-5B), ferf-butyl hypochlorite and W-bromosuccinimide (Section 14-3A). 

Bromomethylbenzo[6]thiophenes are readily obtained in high yields by treatment of the corresponding methyl compound with. V-bromosuccinimide in the presence of benzoyl peroxide.91,105,298 343,4i3,447,487,489-492,517,518 Applied to 3-methylbenzo[6]thiophene, this procedure affords 2-bromo-3-methylbenzo[6]thiophene (12%), in addition to the required product the yield of nuclear substituted product rises to 78% when peroxides are excluded.487 When 3,5-dimethylbenzo[6]thiophene is treated with W-bromosuccinimide, the 3-methyl group is preferentially brominated,489 but in the cases of other 5-alkyl-3-methylbenzo[6]thiophenes inseparable mixtures of products are formed.292 The above reaction has also been applied to... 

In subsequent work, it was found that the reaction conditions could be modified to give a single product. Thus, carrying out the acid-catalyzed cyclization in the presence of an external source of hydride, such as triethylsilane, led to compound 75 in 92% yield, while the presence of an hydride acceptor such as DDQ resulted in the formation of 76 as the sole product, albeit in 45% yield. Compound 77 was finally transformed into the oxindole derivative 79 by oxidation with W-bromosuccinimide in the presence of ferf-butyl alcohol (Scheme 17). 

The quaternary center was constructed stereospecifically by Claisen rearrangement (Scheme 46). The necessary enol ether was obtained by reaction of the secondary alcohol of 399 with ethyl vinyl ether and mercuric acetate. To change the polarity of the endocyclic double bond, the unsaturated ketone was reduced with lithium aluminum hydride to the allylic alcohol, 400, at low temperature. Then, prolonged heating with xylene led to the aldehyde, 401. Protection of the secondary alcohol was achieved by bromoether formation with W-bromosuccinimide in acetonitrile before the aldehyde of 402 was reacted with methyllithium. The epimeric mixture of secondary alcohols was protected as acetates 403. Then, the cyclic ketone... 

The oxidation of p-/ert-butylthiacalix[4]arene or its tetra-O-benzyl ethers generated all four stereoisomers of j-tert-butylsulfinylcalix[4]arenes based on the orientations of the sulfonyl moieties relative the mean plane of the four bridging sulfur centers <03JOC2324>. Alkenes, when treated with W-bromosuccinimide and dimercaptoethane, gave the corresponding... 

The dehydrohalogenation of /3-bromohydroperoxides (Eq. 5) is of historical significance because it constitutes the preparation of the very first stable 1,2-dioxetane (2). We refer to this as the Kopecky method,as illustrated in general terms in Eq. 12. Bromide ion is normally the leaving group, but in isolated cases chlorides and iodides have also been used. The bromohydroperoxides are prepared by electrophilic addition of bromine, usually using l,3-dibromo-5,5-dimethyl-hydantoin (DDH) as a carrier of Br in the presence of concentrated (85-95%) hydrogen peroxide. Other bromine carriers, for example, W-bromosuccinimide (NBS) can also be used. 

Mechanism of benzylic bromination with W-bromosuccinimide. The process is a radical chain reaction and involves a benzylic radical as intermediate. 

Radical substitution I eactions, such as the light-induced chlorination of methane and the allylic bromination of alkenes with W-bromosuccinimide (Review Table 3, reaction 5), are also common. The key step in all these reactions is that a radical abstracts an atom from a neutral molecule, leaving a new radical. 

W-Bromosuccinimide, as brominating agent 649, 650, 654 Bromoxynil 1073, 1350 Brpnsted acidity 498, 499, 507, 524 Brpnsted acids,... 

When dendrobine immonium bromide, prepared by oxidizing den-drobine with W-bromosuccinimide, reacts with methyl bromoacetate under Reformatskii conditions, dendrine of the figured configuration (67) is generated 81). 

Diazomethane itself undergoes transformation to chloro diazomethane at -100 °C, under the influence of f-BuOCl, but the product suffers decomposition with loss of N2 at temperatures above -40 °C.74b Diazocyclopentadiene (14) is perbrominated to 165 using W-bromosuccinimide (NBS).75... 

The literature for other reactions of N-heterocycles with W-bromosuccinimide has been reviewed by Homer and Winkelmann.759... 

These compounds can be prepared by the action of bromine c i a trialkyl phosphite, but a more satisfactory method recently worked out by Goldwhite and Saunders consists in treating the dialkyl hydrogen phosphite with W-bromosuccinimide. In this way dimethyl, diethyl -propyl and isopropyl phosphorobromidates have been obtained as pure liquids by distillation at very low temperature. When kept at ordinary temperatures, they gradually decompose with the evolution of the corresponding alkyl bromide. 

Indole is chlorinated with SOCI2 or aqueous NaOCl to give 3-chloroindole, and 3-bromoindole is formed with W-bromosuccinimide. Action of HNO3 indole causes oxidation of the pyrrole ring followed by polymerization. Indoles substituted in the 2-position react with HNO3 in acetic acid to give 3,6-dinitro compounds. Sulfonation of indole with pyridine-S03 complex leads to the formation of indole-3-sulfonic acid. 

External cooling is now discontinued, and 21.4 g. (0.12 mole) of W-bromosuccinimide[2,5-Pyrrolidinedione, 1-bromo-] (Note 5) is added. Stirring is continued until all of the solid is dissolved ca. 1 hour). The resulting solution, which may be pale yellow, is concentrated with a rotary" evaporator (bath temperature 40-45°) to a volume of about 300 ml. and extracted with five 120-ml. portions of ether. The combined ether extracts are dried over anhydrous magnesium sulfate (20-50 g.), and removal of solvent at reduced pressure provides an oil, which is purified by column chromatography on silica gel (Note 6). Pure bromo-hydrin acetate is obtained as a colorless oil in amounts of up to 26 g., a 65% yield based on farnesyl acetate (Notes 7 and 8). 

---