Cyclooctane

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. 

Suberic Acid. This acid is not produced commercially at this time. However, small quantities of high purity (98%) can be obtained from chemical supply houses. If a demand developed for suberic acid, the most economical method for its preparation would probably be based on one analogous to that developed for adipic and dodecanedioic acids air oxidation of cyclooctane to a mixture of cyclooctanone and cyclooctanol. This mixture is then further oxidized with nitric acid to give suberic acid (37). 

Examine the following thermochemical data pertaining to hydrogenation of unsaturated eight-membered ring hydrocarbons to give cyclooctane ... 

For cyclooctane, a total of 11 conformations have been suggested for consideration and their relative energies calculated. The boat-chair was calculated to be the most stable conformation. This prediction was confirmed by analysis of the temperature dependence of the F-NMR spectra of fluorocyclooctanes. The activation energy for interconversion of conformers is 5-8 kcal/mol. A few of the most stable conformations are shown below. 

Saturated hydrocarbons such as neopentane, notbomane, and cyclooctane have been converted to the corresponding perfluoro derivatives in 10-20% yield by gas-phase reaction with fluorine gas diluted with helium at —78°C. Simple ethers can be completely fluorinated under similar conditions. Crown polyethers can be fluorinated by passing an Fa/He stream over a solid mixture of sodium fluoride and the crown ether. Liquid-phase fluorination of hydrocarbons has also been observed, but the reaction is believed to be ionic, rather than radical, in character. A variety of milder fluorination agents have been developed for synthetic purposes and will be discussed in Chapter 6 of Part B. 

Intramolecular hydrogen abstraction reactions have also been observed in mediumsized rings. The reaction of cyclooctene with carbon tetrachloride is an interesting case. As shown in the equation below, whereas bromotrichloromethane adds to cyclooctene in a completely normal manner, carbon tetrachloride gives some 4-chloro-l-trichloromethyl-cyclooctane as well as the expected product ... 

Cyclooctane-l,5-diyl-bis(pyrazol-l-yl)borate (L) with cobalt(II), nickel(II), and zinc(II) nitrates gives [(j -L)M] (M = Co, Ni, Zn) strongly stabilized by the C—H M agostic interactions, which justifies their inclusion in the class of organometallic complexes [89AGE205, 91ICA(183)203, 92IC974]. 

In the procedure given here, the reaction is applied to a cyclic alcohol to produce a bridged ether. The product is of interest in that it can be cleaved to produce disubstituted cyclooctanes of known geometry (cf. Chapter 6, Section V). 

Cyclooctane Sulfide (9-Thiabicyclo[3.3.1]nonane) from 1,5-Cyclooctadiene... 

Cyclooctane Sulfide To 12.5 g (0.06 mole) of the dichlorosulfide in 150 ml of ether is added 1.2 g (0.03 mole) of lithium aluminum hydride in 60 ml of ether at a rate so as to maintain a gentle reflux (about 20 minutes). The mixture is allowed to stand overnight and is then cautiously treated with water to decompose the excess hydride. The mixture is mixed with fuller s earth (Floridin) and is filtered, and the filtrate is dried over anhydrous magnesium sulfate. Filtration of the solution and evaporation of the solvent (rotary evaporator) gives about 7 g of the colorless crystalline solid, mp 170-171°. It may be recrystallized from aqueous methanol, mp 172-173°. 

Cyclononane, strain energy of, 114 Cyclooctane, strain energy of, 114 Cyclooctatetraene, bond lengths in, 524... 

The alicyclic analogs 4 with hydrogen bromide in diethyl ether at room temperature behave similarly to yield the 4,5-fused 7-bromo-3/7-azepin-2-amines 5 as their hydrobromide salts. Yields are high except for the cyclooctane derivative (n = 4). Once again, the free bases are liberated by treatment with sodium hydrogen carbonate. 

An illustrative example of the potency of the second-generation Ru catalyst C is found in Paquette s highly efficient total synthesis of the natural products teubrevin G (122) and teubrevin H (123), which feature a cyclooctane core fused and spiroannulated to smaller oxygen-containing rings [76]. In the retrosyn-thetic analysis, the viability of an RCM step for annulation of a cyclooctenone ring to the furan played a central role. 

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