Cyclooctene, reaction

Equimolar amounts of cyclopentene and cyclooctene as well cyclohexene and cyclooctene were mixed and kept ready for the experiments (Table 2). Experiments were carried out for 20 hours, however, the cyclohexene/cyclooctene reaction was carried out for 5.5 hours for measurements of initial hydrogenation yields of the binary mixture system which indicated a higher hydrogenation yield for cyclohexene than for cyclooctene. 

The Cyclooctene Isomerization. A reaction that attracted some attention in recent years is the cis-trans isomerization of cyclooctene [84]. The cis isomer is much less strained than the trans, but the latter is readily fonned upon direct photolysis and also upon photosensitization. In this case, two enantiomeric trans isomers are formed. The appropriate loop is a variation of that shown in Figure 14, as shown in Figure 34. This is a phase inverting i -type loop, that... 

A mixture of 0.20 mol of the adduct from cyclooctene and dibromocarbene (note 1) and 250 ml of dry diethyl ether was cooled to -65°C. A solution of 0.23 mol of ethyllithium (note 2) in 200 ml of diethyl ether (see Chapter II, Exp. 1) was added in 15 min with cooling between -60 and -50°C. The reaction was very exothermic (note 3). After the addition the cooling bath was removed and the temperature was allowed to rise to about -10°C and the reaction mixture was poured into 200 ml of ice-water. The aqueous layer was extracted twice with diethyl ether. After drying, the solvent was removed in a water-pump vacuum and the remaining liquid was distilled through a 40-cm Vigreux column. 1,2-Cyclononadiene, b.p. 62°C/22 mmHg, 1.5059, was obtained in 86 yield. 

The reaction of thiocyanogen (N=CS—SC=N) with cis cyclooctene proceeds by anti addition... 

Reaction of cyclooctene with trifluoroacetic acid occurs by a Itydride-shift process. 

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 ... 

Reaction of [( 7 -l,3-r-Bu2C5H3)(OC)2Fe-P(SiMe3)P = C(SiMe3)2] with [(cyclooctene)Cr(CO)5] yields the sandwich having the rf rj coordination... 

A mixture of 17 g of the methiodide and 32 ml of a 40 % aqueous potassium hydroxide solution is heated with stirring in a flask fitted with a condenser. The heating bath should be kept at 125-130°, and the heating should be continued for 5 hours. The cooled reaction mixture is then diluted with 30 ml of water and washed twice with 25-ml portions of ether. The aqueous layer is cautiously acidified in the cold with concentrated hydrochloric acid to a pH of about 2 and then extracted five times with 25-ml portions of ether. The combined extracts are washed twice with 10% sodium thiosulfate solution and are dried (magnesium sulfate). Removal of the solvent followed by distillation affords about 3 g of 4-cyclooctene-l-carboxylic acid, bp 125-12671-1 mm. The product may solidify and may be recrystallized by dissolution in a minimum amount of pentane followed by cooling in a Dry-Ice bath. After rapid filtration, the collected solid has mp 34-35°. 

Treatment of ris-cyclooctene oxide (15) with lithium diethylamide in ether at reflux gave endo-ris-bicyclo[3.3.0]octan-2-ol (16) in 70% yield. Under identical conditions, trons-cyclooctene oxide (17) gave exo-as-bicyclo[3.3.0]octan-2-ol (18) in 55-60% yield (Scheme 5.6) [7]. In each case, the reaction is completely stereospe-cific, with neither of the epimeric alcohols being observed, which suggests that the reactions proceed through insertion of a carbenoid (rather than the same a-li-... 

Steric factors may also be important in situations where alternative modes of reaction are available. Dall Asta (44) examined the ring-opening polymerization of 3-methyl-m-cyclooctene. By infrared analysis of the product formed, he obtained quantitative information about the occurrence of head-to-head and head-to-tail successions. More than 90% of the links in the polymethyloctenamer were of the head-to-tail type, but the sterically more hindered and, therefore, unfavored head-to-head links were also observed (about 5%). Ofstead (39) investigated the ring-opening polymerization of some 1,5-cyclooctadienes substituted at one of the two... 

Catalytic cyclopropanation of alkenes has been reported by the use of diazoalkanes and electron-rich olefins in the presence of catalytic amounts of pentacarbonyl(rj2-ris-cyclooctene)chromium [23a,b] (Scheme 6) and by treatment of conjugated ene-yne ketone derivatives with different alkyl- and donor-substituted alkenes in the presence of a catalytic amount of pentacarbon-ylchromium tetrahydrofuran complex [23c]. These [2S+1C] cycloaddition reactions catalysed by a Cr(0) complex proceed at room temperature and involve the formation of a non-heteroatom-stabilised carbene complex as intermediate. 

At this point the catalytic process developed by Dotz et al. using diazoalkanes and electron-rich dienes in the presence of catalytic amounts of pentacar-bonyl(r]2-ds-cyclooctene)chromium should be mentioned. This reaction leads to cyclopentene derivatives in a process which can be considered as a formal [4S+1C] cycloaddition reaction. A Fischer-type non-heteroatom-stabilised chromium carbene complex has been observed as an intermediate in this reaction [23a]. 

The complex [Ir(CO)(CjH,4)2Cl]2 (CgHi4 = cyclooctene) also oxidatively adds RCOCl to yield R2lr2(CO)4Cl4 (XXXII R = Me, Et, I -Pr, or Ph) (7, 215). Evidence suggests a two-step reaction, the second step... 

Addition of TCS 14 to CH2l2/Zn, which contains up to 0.04 mol% of lead impurity, improves the Simmons-Smith reaction of olefins such as cyclooctene to give up to 96% of the cyclopropane 2103 [36] (Scheme 13.12). 

The hydrogenation activity of the isolated hydrides 3 and 6 towards cyclooctene or 1-octene was much lower than the Wilkinson s complex, [RhCKPPhj) ], under the same conditions [2] furthermore, isomerisation of the terminal to internal alkenes competed with the hydrogenation reaction. The reduced activity may be related to the high stability of the Rh(III) hydrides, while displacement of a coordinated NHC by alkene may lead to decomposition and Rh metal formation. 

Bidentate NHC-Pd complexes have been tested as hydrogenation catalysts of cyclooctene under mild conditions (room temperature, 1 atm, ethanol). The complex 22 (Fig. 2.5), featuring abnormal carbene binding from the O carbon of the imidazole heterocycles, has stronger Pd-C jj, bonds and more nucleophilic metal centre than the bound normal carbene chelate 21. The different ligand properties are reflected in the superior activity of 22 in the hydrogenation of cyclooctene at 1-2 mol% loadings under mild conditions. The exact reasons for the reactivity difference in terms of elementary reaction steps are not clearly understood [19]. 

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