Cyclooctene: hydroxylation

The hydroxyl group in /raw.v-cycloocten-3-oI determines the stereochemistry of reaction of this compound with the Simmons-Smith reagent. By examining a model, predict the stereochemistry of the resulting product. 

The following alkenes have been hydroxylated by these methods (method, stirring time, yield %) dicyclopentadiene (A, 4 hours, 86%) oct-l-ene (A, 2 hours, 85%) (1) cyclohexene (B, 1 hour, 86%) cyclooctene (B, 1 hour, 73%). 

The opening move was the transformation of the known glucopyranoside 355 into exomethylene vinylpyranose 356. TIBAL-promoted Claisen rearrangement of 356 provided the cyclooctene derivative 357 almost quantitatively, which was then transformed to protected cyclooctanose 358 by methylation followed by hydroboration-oxidation. Installation of the hydroxymethyl function at C5 required three further operations oxidation of the Cs-hydroxyl, Tebbe methylenation, and hydroboration-oxidation. In the event, a mixture of epimeric... 

Thus, the substituted heteropolyanion is stable and active even in the presence of oxidants such as /-BuOOH or PhIO. Note that the heteropolyanion is unstable with respect to hydrogen peroxide. Based on the high stability, TMSP can be used for alkane hydroxylation [67b]. Mansuy et al. have reported that P2Wn06i (Mn3+ Br)8 is oxidation resistant and more active for the epoxidation of cyclooctene with PhIO than those containing Fe3+, Co2+, Ni2+, or Cu2+ [68]. The oxygenations of cyclohexane, adamantane, and heptane and the hydroxylation of naphthalene, are also catalyzed by TMSP. 

Oxymercaration (2, 265-267 3. 194). Brown and Geoghegan have investigated the relative reactivities of a number of olefins in the oxymercuration reaction in a 20 80 (v/v) mixture of water and THF. The following reactivity is observed terminal disubstituted > terminal monosubstituted > internal disubstituted > internal trisub-stituted > internal leirasubstitu ted. Thus steric factors play a major role in the reactivity of olefins. Increased substitution on the double bond and increased steric hindrance at the site of hydroxyl or mercury substituent attachment decrease the rate of reaction. In the case of olefins of the type RCH CHR, cts-oleiins are more reactive than the corre.sponding rra/i.s-olefins. Inclusion of the double bond in ring systems causes a moderate rate increase which varies somewhat with structure cyclohcxenc > cyclo-pentenc cyclooctene norbornene bicyclo[2.2.2]-octene-2. 

Cyclooctene treated with TBHP and ebselen gave the epoxide accompanied by trace amounts of 3-hydroxycyclo-octene resulting from a-hydroxylation <2001MI74>. Aromatic aldehydes with electron-donating substituents were... 

The 1,4-elimination of 193, given in the Eqs. 52 and 53, represents two pathways leading to two different iminium ions 194 and 195, whose relative distribution will depend on whether the reaction is performed under thermodynamic or kinetic control. The species 194 is a cyclooctene derivative and the species 195 a cyclohexane derivative. The cyclohexane derivative 195 must, of course, predominate in a thermodynamically controlled reaction. Like the species 193, the species 196 also represents two pathways for 1,4-elimination as shown in Eqs. 54 and 55. Fortunately, both the pathways yield the same product 197. The reactions shown in Eqs. 56 and 57 are examples of elimination resulting from the 1,3-diol mono-tosylate system. An electron pair orbital on the hydroxylic oxygen that is antiperiplanar to the cleaving central ac c bond provides the necessary electronic push in which the former makes the latter weak, and therefore labile for cleavage. The reaction shown in Eq. 57 was used by Corey and coworkers in a synthesis of... 

The reaction course taken by photoexcited cycloalkenes in hydroxylic solvents depends on ring size. Cyclohexene, cycloheptene, cyclooctene, 1-methylcyclohexene,... 

The photocycloaddition of tetronates is analogous to that of vinylgous esters as P-diketone equivalents (vide supra). The MEM-protected tetronate 155 is irradiated in the presence of cyclopentene, cyclohexene and cw-cyclooctene, and the resulting adducts 156 are immediately deprotected with titanium tetrachloride to give the hydroxyl lactones 157 as mixture of diastereomers in about 50% yield. These adducts are subjected to cesium carbonate in THF under microwave irradiation to give the ring-opened oxepanediones 158 in 74-84% yield. 

Syn-hydroxylation of olefins has also been carried out with KMnO solution using a PTC catalyst under alkaline conditions. Thus, under alkaline conditions, cyclooctene gives 50% yield of cis 1,2-cyclooctane diol compared to an yield of about 7% by the classical technique (Scheme 72). 

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