1.3- Cyclooctadiene oxidation

Cyclohexadiene oxide 13 is very reactive toward hydronium ion-catalyzed hydrolysis the bimolecular rate constant for acid-catalyzed hydrolysis kH - 1.6 x 104M 1 s. General acid catalysis by dihydrogen phosphate or other general acids was not observed in the hydrolysis of 1,3-cyclooctadiene oxide 11, which is much less reactive toward hydronium ion-catalyzed hydrolysis (fcH = 3.6 s 1 at 25 °C) than 13.36a The magnitude of general acid catalytic... 

Two examples using i-BuLi/(—)-sparteine mixture as base have been reported to promote effective allylic alcohols formation in moderate ee for the spiro epoxide 82 and cyclooctadiene oxide 83 ° (Scheme 33). In the last case, such regioselectivity could be explained by the relatively flat conformation of the medium-sized oxirane which favors the syn base-oxirane complex (see Section n.A). 

In order to broaden the scope of asymmetric transannular rearrangement, functionalised raeso-epoxides derived from medium-sized cycloalkenes have been studied. Protected diol derivatives of cyclooctadiene oxide were used as the... 

Low oxidation states - An important characteristic of transition metal chemistry is the formation of compounds with low (often zero or negative) oxidation states. This has little parallel outside the transition elements. Such complexes are frequently associated with ligands like carbon monoxide or alkenes. Compounds analogous to Fe(CO)s, [Ni(cod)2] (cod = 1,4-cyclooctadiene) or [Pt(PPh3]3] are very rarely encountered outside the transition-metal block. The study of the low oxidation compounds is included within organometallic chemistry. We comment about the nature of the bonding in such compounds in Chapter 6. 

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. 

If the insertion step following oxidative addition occurs on one of the two fragments resulting from oxidative addition, an intramolecular catalytic reaction (C—O — C—C rearrangement) takes place (example 40, Table III). It is interesting to note that two different products—2,6- and 3,6-heptadienoic acids—can be obtained from allyl 3-butenoate. Their ratio can be controlled by adding 1 mole of the appropriate phosphine or phosphite to bis(cyclooctadiene)nickel or similar complex. Bulky ligands favor the 2,6 isomer. It is thus possible to drive the reaction toward two different types of H elimination, namely, from the a or y carbon atoms. 

Some typical results are shown in Table 2. The table shows that oxidation of conjugated dienes such as isoprene, piperylene (1,3-pentadiene), cyclopentadiene and 1,3-cyclohexadiene with a carbon anode in methanol or in acetic acid containing tetraethylammonium p-toluenesulfonate (EtjNOTs) as the supporting electrolyte yields mainly 1,4-addition products2. 1,3-Cyclooctadiene yields a considerable amount of the allylically substituted product. 

Cation-radicals, stabilized in zeolites, are excellent one-electron oxidizers for alkenes. In this bimolecular reaction, only those oxidizable alkenes can give rise to cation-radicals, which are able to penetrate into the zeolite channels. From two dienes, 2,4-hexadiene and cyclooctadiene, only the linear one (with the cylindrical width of 0.44 nm) can reach the biphenyl cation-radical or encounter it in the channel (if the cation-radical migrates from its site toward the donor). The eight-membered ring is too large to penetrate into the Na-ZSM-5 channels. The cyclooctadiene can be confined if the cylindrical width is 0.61 nm, however the width of the channels in Na-ZSM-5 is only 0.55 nm. No cyclooctadiene reaction with the confined biphenyl cation-radical was detected despite the fact that, in solution, one-electron exchange between cyclooctadiene and (biphenyl) proceeds readily (Morkin et al. 2003). 

In the first total synthesis of kelsoene (rac-l) [7, 8], commercially available 1,5-cyclooctadiene (11) was chosen as the starting material (Scheme 3). Oxidative cyclization with a mixture of PdCl2 and Pb(OAc)4 in acetic acid led to the formation of a diquinane diacetate [13] that was saponified to give... 

Ketone rac-13 was transformed into the corresponding silylenolether and by Pd(II)-mediated Saegusa oxidation [14] into a, -unsaturated ketone rac-14. By alkylative enone transposition comprising methyl lithium addition and pyridinium chlorochromate (PCC) oxidation [15], rac-14 was finally converted into the racemic photo cycloaddition precursor rac-6. In conclusion, the bicyclic irradiation precursor rac-6 was synthesized in a straightforward manner from simple 1,5-cyclooctadiene (11) in nine steps and with an overall yield of 21%. 

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