1,5-Cyclooctadiene, bromination

Bis(bexacbIorocycIopentadieno)cycIooctane. The di-Diels-Alder adduct of hexachlorocyclopentadiene [77 7 ] and cyclooctadiene (44) is a flame retardant having unusually good thermal stabiUty for a chlotinated aUphatic. In fact, this compound is comparable ia thermal stabiUty to brominated aromatics ia some appHcations. Bis(hexachlorocyclopentadieno)cyclooctane is usedia several polymers, especially polyamides (45) and polyolefins (46) for wire and cable appHcations. Its principal drawback is the relatively high use levels required compared to some brominated flame retardants. 

Cyclooctadiene is reacted with bromine to make fire-retardants. Cyclododecane is oxidized with air and then nitric acid to make a diacid containing 12 carbons. This acid is used to prepare some types of nylon, and its esters are used in synthetic lubricating oils. 

Regioselective electrophilic bromination of the carbazole 1025 afforded the 6-bromocarbazole 1026. Cleavage of the methyl ether to 1027 and subsequent nickel-mediated coupling using a dimeric 7i-prenylnickel bromide complex prepared in situ from prenyl bromide 925 and bis(l,5-cyclooctadiene)nickel(0) led directly to siamenol (89) (546) (Scheme 5.151). 

Since the reactivity of double bonds in electrophilic bromination increases drastically with increasing alkyl substitution, selective monoaddition to the more substituted double bond in nonconjugated dienes can be accomplished with pyridin hydrobromide perbromide.264 Chlorination265 and bromination266 of c/s,cis-1,5-cyclooctadiene lead to the expected dihalogen and tetrahalogen derivatives. 

Thiiranes can be formed directly and stereospecifically from 1,2-disubstituted alkenes by addition of trimethylsilylsulfenyl bromide, formed at -78 C from reaction of bromine with bis(trimethylsilyl) sulfide (Scheme 7).12 A two-step synthesis of thiiranes can be achieved by addition of succinimide-A/-sulfe-nyl chloride or phthalimide-A -sulfenyl chloride to alkenes followed by lithium aluminum hydride cleavage of the adducts (Scheme 8).13 Thiaheterocycles can also be formed by intramolecular electrophilic addition of sulfenyl chlorides to alkenes, e.g. as seen in Schemes 914 and 10.13 Related examples involving sulfur dichloride are shown in Schemes 1116 and 12.17 In the former case addition of sulfur dichloride to 1,5-cyclooctadiene affords a bicyclic dichloro sulfide via regio- and stereo-specific intramolecular addition of an intermediate sulfenyl chloride. Removal of chlorine by lithium aluminum hydride reduction affords 9-thiabicyclo[3.3.1]nonane, which can be further transformed into bicyclo[3.3.0]oct-1,5-ene.16... 

Iodine, less reactive than bromine, is best added to alkenes by use of IC1 and IBr (see Section 1.8.3.3). Iodine itself adds rapidly but reversibly to alkenes forming diiodides by mechanisms that can be either ionic or radical. The position of the equilibrium depends upon the structure of the alkene, the solvent and the temperature. Simple vicinal diiodides survive distillation in the dark, but are unstable toward iodine or radicals. In the presence of functions containing free OH groups, such as alumina, HI generated from I2 adds to alkenes irreversibly with the result that the HI adduct, rather than the I2 adduct, is the exclusive product.86 A comparison of the reaction of 1,5-cyclooctadiene with chlorine, bromine and iodine in CH2CI2 reveals that chlorine gas at-50 C gives a 93 7 mixture of trans- and cis-5,6-dichlorocyclooc-... 

The present two-step procedure for the synthesis of 1,3,5-cyclooctatriene uses commercially available 1,5-cyclooctadienes as starting material. Although allylic bromination of 1,5-cyclooctadiene with N-bromosuccinimide produces a mixture of 3-bromo-1,5-cyclooctadiene and 6-bromo-1,4-cyclooctadiene,2 dehydrobromination of this mixture with UCI-IJ2CO3/DMF affords only 1,3,5-cyclooctatriene, which is in equilibrium with its valence isomer bicyclo[4.2.0]octa-2,4-diene. 

Monochloborane-dimethyl sulfide coexists with small amounts of the borane and dichloroborane complexes, but the bromoborane-dimethyl sulfide complex appears to be almost pure. - These complexes react readily with alkenes at 25 °C and can be used for hydroborations in a variety of solvents. Dialkylha-loboranes are obtained in high yield as their dimethyl sulfide complexes (equation 24), but dimethyl sulfide is readily removed under reduced pressure if required. - The reagents are also useful for cyclic hydroborations of dienes such as cyclooctadiene (equation 25). An alternative approach to dialkylbro-moboranes involves the reaction of dialkyl(methylthio)boranes with bromine. ... 

The application of Hofmann s degradation to iV-methylgranatanine (XXXIII) gives rise in the firsts step to a des-dimethylgranatanine, b.p. 89.5-92°/14.5 mm., d° 0.916, which forms a picrate, m.p. 155°, a chloro-platinate, m.p. 178-180° (dec), and a methiodide, m.p. 264° (dec) (221). The quaternary hydroxide (XXXIV) corresponding to des-dimethylgranatanine methiodide is decomposed by heat into trimethylamine and A -cyclooctadiene (XXXV), b.p. 39.5°/16.5 mm. Although the sole product of the ozonization of the hydrocarbon is succindialdehyde (232), which indicates A -cyclooctadiene (XXXVI), it has been sho vn to consist of a tautomeric mixture of the two forms. It absorbs bromine readily, but. 

Bromination of 1,5-cyclooctadiene with A -bromosuccinimide (NBS) gives a mixture of two constitutional isomers of CgHnBr. Suggest reasonable structures for these two isomers. 

No product derived from the transannular hydrogen abstraction is observed in the addition of bromotrichloromethane, because bromine atom abstraction is sufficiently rapid to prevent effective competition by the hydrogen-abstraction process. Another example of transannular cyclization of unsaturated radicals is found in the reaction of 1,4-cyclooctadiene with acetaldehyde in the presence of benzoyl peroxide, which gives a cyclized ketone by a process involving an intramolecular addi-... 

Organic Chlorine. This is a good flame retardant, less expensive but less efficient than bromine. It too is greatly synergized by antimony trioxide. A particularly popular compound is Dechlorane Plus, the adduct of hexachlorocyclopentadiene with cyclooctadiene. Chlorinated paraffins are also widely used. Like bromine, chlorine may be limited by problems with smoke, toxic corrosive gases, and environmental concerns. 

Ong and co-workers reported an alternative synthesis of poly(3,6-dialkylthieno[3,2- ]thiophene-co-bithiophene) (Scheme 17.7) [50]. In this case, a symmetrical monomer was constructed from the Stille cross-coupling of 2,5-dibromo-3,6-dialkylthieno[3,2- ]thiophene with 2-tributylstannylthiophene followed by bromination in the free a-positions with iV-bromosuccinimide. Dehalogenative polymerization (often termed Yamamoto polymerization [86]) was performed by refluxing in toluene in the presence of excess bis(cyclooctadiene)nickel(0) and 2,2 -bipyridyl afforded the product in 92 % yield. The number-average molecular weight was 12400 gmoP with a polydispersity of 1.6. 

The copolymer is not strictly alternating, since MA seems only to be incorporated in the intermolecular step the intramolecular step being a transannular reaction of the cyclooctadiene. On the basis of composition, IR and NMR studies, and failure of the polymer to take up bromine, a... 

Allylic Bromination of Alkenes. The alcohols (1) were converted into the rearranged primary allylic bromides (2) via Sn2 displacement by treatment with NBS/Me2S (eq 29). A well researched procedure for the allylic bromination of 1,5-cyclooctadiene has also appeared. NBS and water react with allylic ethers to regenerate alcohols. ... 

Yamago developed a conceptually different synthetic route and demonstrated the selective synthesis of [8]CPP, which was the smallest CPP prepared at that time (Scheme 6.2c) [16]. The synthesis utilized the cis coordination of bisaryl platinum complexes as a structural motif for making a cyclic structure, and platinum square 14 was prepared by transmetallation of 4,4 -bisstannylated biphenyl 13c (X = SnMe3) and Pt(cod)Cl2 (cod refers to 1,5-cyclooctadiene). Compound 14 was also prepared stepwise by transmetallation of 13c to bisplatinum 13d and subsequent reaction between 13c,d. Once 14 was formed, ligand exchange from cod to dppf [dppf refers to l,3-bis(diphenylphosphino)ferrocene] and subsequent reductive elimination of platinum by employing bromine afforded [8] CPP. 

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