Cyclooctatetraene 1,3,5 -Cycloocta triene

The diastereoselectivity in the reaction of 42 was proven to be independent of the polarity of the solvent used and is therefore considered a consequence of steric factors [34a], Photo-oxygenation of 1,3,5-cycloocta-triene [35] affords both the bicyclic and tricyclic endoperoxides (isolated yield 20 and 5%, respectively) as found for the heptatriene 39a, while for cyclooctatetraene [36] only the bicyclic peroxide is obtained in 26% yield. 

Dehydrogenation cf. 4, 485). Causing and Wilke have reported two high-yield preparations of cyclooctatetraene. Reaction of 1,5-cyclooctadiene (1) and -butyllithium-TMEDA in a ratio of 1 3 gives the crystalline compound 2 in practically quantitative yield. Cyclooctatetraene (3) is obtained from 2 by oxidation with CdCl2. The intermediate 2 can also be obtained from 1,3,6-cycloocta-triene, but not from 1,3-cyclooctadiene or 1,3,5-cyclooctatriene. 

It is possible in principle to deduce from the position of the first absorption band the twisting angle between the double bonds in cyclic conjugated polyenes, e.g. on the basis of a simple LCBO model50. This has been attempted for cycloocta-l,3,5-triene 184257 and cyclooctatetraene 239260. For the former it was deduced that the --system becomes... 

A mixture of cycloocta-l,3,5-triene and cycloocta-l,3,6-triene formed by partial reduction of cyclooctatetraene is the usual starting point for the study of cyclooctatriene complexes, and obviously complexes may be derived from both isomers. Also, the 1,3,5-isomer is in thermal equilibrium with its valence tautomer, bicyclo[4.2.0]octa-2,4-diene (XXVII), at 100° C (30), from which complexes may also be formed. Although silver nitrate... 

Dicyclopentadiene has two cyclopentene rings with different reactivities. In the reaction with nickel complexes and carbon dioxide only the more reactive norbornene ring couples with CO2, whereas the unstrained ring proved to be unreactive [14,16]. The last example in Figure 6 is cyclooctatetraene, which stands in a temperature-dependent equilibrium with bicyclo[4.2.0]octatriene. Both isomers undergo an oxidative coupling with nickel and CO2. Decomposition by hydrochloric acid leads to cycloocta-2,4,6-triene-carboxylic acid and bicyclo-[4.2.0]octa-2,4-diene-7-carboxylic acid [14]. 

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