Trans-3- cyclohexene: Mercury

The preparation of Pans-1,2-cyclohexanediol by oxidation of cyclohexene with peroxyformic acid and subsequent hydrolysis of the diol monoformate has been described, and other methods for the preparation of both cis- and trans-l,2-cyclohexanediols were cited. Subsequently the trans diol has been prepared by oxidation of cyclohexene with various peroxy acids, with hydrogen peroxide and selenium dioxide, and with iodine and silver acetate by the Prevost reaction. Alternative methods for preparing the trans isomer are hydroboration of various enol derivatives of cyclohexanone and reduction of Pans-2-cyclohexen-l-ol epoxide with lithium aluminum hydride. cis-1,2-Cyclohexanediol has been prepared by cis hydroxylation of cyclohexene with various reagents or catalysts derived from osmium tetroxide, by solvolysis of Pans-2-halocyclohexanol esters in a manner similar to the Woodward-Prevost reaction, by reduction of cis-2-cyclohexen-l-ol epoxide with lithium aluminum hydride, and by oxymercuration of 2-cyclohexen-l-ol with mercury(II) trifluoro-acetate in the presence of ehloral and subsequent reduction. ... 

Method D (equation 37) is neither a convenient nor an effective way to generate 3a. After heating bis[bromo(trimethylsilyl)methyl]mercury for 7 days at 160 °C with cyclohexene and diphenylmercury, 7-trimethylsilylbicyclo[4.1.0]heptane was obtained in a yield of only 9%, accompanied by a trace of the carbene dimers (cis- and trans-bis(trimethylsilyl)ethene) and a large amount of starting material75. 

Utley and coworkers [31,32] reported that the stereoisomeric ratio cis/trans) of 1,4-disubstituted cyclohexanes formed by the hydrogenation of the corresponding activated cyclohexenes at a mercury electrode depended on solvents and proton sources, and discussed the stereochemical mechanism in detail. On the other hand, according to Lessard and coworkers [33,34], the hydrogenation at a Raney nickel electrode always provides the trans isomers in excess. 

Oxymercuration (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 tetrasubstituted. 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, civ-olefins are more reactive than the corresponding trans-olefins. Inclusion of the double bond in ring systems causes a moderate rate increase which varies somewhat with structure cyclohexene > cyclo-pentene cyclooctene norbornene bicyclo[2.2.2]-octene-2. 

The most reactive and successful homogeneous C—H activation catalyst to date is [RhCl(CO)(PMe3)2]- Under irradiation with a 100 W high-pressure mercury lamp and in a nitrogen atmosphere, the complex converts cyclohexane to cyclohexene (168 turnovers in 16.5 h) and traces of benzene, and n-hexane gives mainly 2-hexene (155 turnovers in 27h, cis trans = 3). The removal of H2 by flushing with N2 improves the conversion rate. All reactions proceed at room... 

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