Cyclooctane, reaction

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 ... 

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). 

Fig. 20, The optical spectrum of the products of a AgiCgH, (cyclooctane) = 1 10 cocondensation reaction, (A) after deposition at 10-12 K, and (B)-(D) after 15-, 30-, and 60-min, narrow-band (8 nm), 335-nm, continuous excitation (152).

The transformation of the catalytically active species (21 or 24) into the complex (19) at the end of the catalytic reaction requires the abstraction of a hydrogen atom from the cyclooctene dimer and is accompanied by hydrogenation of the monomer to give cyclooctane [Eq. (5)] ... 

A seven-membered ring is formed in the cyclization of 195 (equation 95)105. The homologue 196 affords the fused cyclooctane 197, together with the cis- and trans-decalinones 198 (equation 96)106. Six-, seven- and eight-membered rings are produced in Lewis acid-catalysed reactions of various cyclohexenones with side-chains terminating in allylic trimethylsilyl groups (equations 97 - 99)107. 

This formed a basis for the study of the H2 addition step in a precatalyst for Ir enantioselective hydrogenation [70]. By NMR, it proved possible to characterize a single diastereomer of the initial addition product at -40°C in THF, the configuration of which was defined by nOe methods. This was converted into a mixture of two diastereomers of the disolvate dihydride with release of cyclooctane at 0°C. In all cases, H trans-N is preferred over H trans-P, as was originally observed by Crabtree. The investigations were completed by DFT computational studies on the initial steps of the reaction sequence as a model for the stereose-... 

Transannular reactions have also been described in cyclooctane series. For example, cyclooctane oxide combines with formic acid to form two glycols by such reaction. 

The thermolysis of the bicyclodiene 109 at 225 °C gives rise to equilibrium mixture of cyclooctatriene and its transformation products (see below)54. More recently the influence of a methoxy group on the thermal behavior of the bicyclo[5.1.0]octa-2,4-diene system was studied56. Heating of 8-ewdo-methoxydiene 115 in cyclooctane at 95 °C gaves rise to methoxy substituted diene 117 and not to the product 116 of butadienylcyclopropane rearrangement (equation 41). The thermolysis of the 8-exo-isomer 118 has taken place as an equilibrium reaction to give 6-ewdo-methoxy diene 119 (equation 42)56. These two reaction partners were separated by TLC. 

Butyl acrylate. 1-hexene was used as the starting material. After 15 h the reaction mixture contained n-hexyane and 1-hexene 2-hexenes 3-hexenes in a 1 10 1 ratio. Product is a mixture of cyclooctene (ca. 99%) and cyclooctane. From [161]. 

Side reactions that occur with intramolecular cycloaddition, such as linear oligomerization or dimerization of the nitrile oxide, are not very common when shorter chain lengths n < 1) are used due to the entropically favored intramolecular process. A rather unusual result in this regard involves the formation of a fused cyclooctane instead of the less-strained six-membered ring (also fused) in the cycloaddition of the nitrile oxide derived from p-naphthoquinone (Scheme 6.43). This result is consistent with the effect of electron-withdrawal in the enedione part, leading to increased reactivity (247), and also reflects the known sluggishness of cyclohexenes towards nitrile oxides (cf. Section 6.2.1.2). 

The photodecomposition of -alkanes at excitation energies slightly above the absorption onset involves both C-H and C-C bond decompositions [18]. The dominant process is the C-H scission, (H2) 0.8-0.9, and the contribution of C-C decomposition is small. In the photolysis of cyclohexane, cycloheptane, cyclooctane, and cyclodecane, however, only hydrogen evolution was observed [[Pg.375]

The compound selected to illustrate this procedure is Cr(rj6-C6H5C02CH3)(C0)2(CNC0C6H5). Compounds of this type have already been shown to be active catalytically but sometimes with a different activity from that of the well-known parent tricarbonyl derivatives.4 For example, reaction of cis-cyclooctene with Cr( 6-l-C02CH3-2-CH3C6H4)(C0)2-(CNCOC6H5) for 15 h at 60 °C in CCl4-tetrahydrofuran (THF) solution affords 60% conversion into l-chloro-2-(trichloromethyl)cyclooctane.2... 

This greater resistance of the thienyl system to ring opening is reflected in the fact that this carbene is captured more efficiently (27%) by cyclooctane than is the furyl-carbene (7%). Only dimeric products were obtained from the carbene (375) attached to position 3 of thiophene no ring fragmentation was observed (Scheme 119). The reactions of some other carbenes derived from diazomethylthiophenes have been referred to in Section 3.14.2.2. 

The reaction of 1,2-dicarbonyl compounds with amidrazones, semicarbazide, thiosemicarbazide and aminoguanidine has also been used for the synthesis of condensed 1,2,4-triazines. Cyclohexane-, cycloheptane- and cyclooctane-1,2-diones (489) with amidrazones (453) afford the cycloalkatriazines (490) (78HC(33)189, p.66l). 

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