Bicyclo octane, chlorination

The cyclohexasilane ring of trans-lfl has a chair form and both chlorine atoms occupy axial positions. The cyclotetrasilane ring has a folded structure with the fold angles of 33.0 and 33.6°. The structure of the silicon framework of trans-lfl resembles that of bicyclo[4.2.0]octane, in which the cyclohexane ring has a chair form and the cyclobutane ring has a folded structure.67... 

The novel arenium ion 95 was synthesized266 by one-electron oxidation of the triphenylene-based starting compound to form a radical cation which abstracted a chlorine atom with a concomitant rearrangement to yield the hexachloroantimonate salt. The arenium ion character is apparent from the 13C spectrum (three signals at 813C 212.9, 187.6, and 173.6) and from the bond distances, which are very close to those shown for ion 91. Cation 95 can be stored at room temperature for months. This exceptional stability was attributed to the annelation to the two bicyclo[2.2.2]octane units and the spiroconjugation effect of the fluorenyl moiety.267... 

Furthermore, di- and polychlorination are much less prevalent. Dicarboxylic acids are predominantly chlorinated in the middle of the chain, and adamantane and bicyclo[2.2.2]octane at the bridgeheads by this procedure. The reasons for the high co - 1 specificity are not clearly understood. Alkyl bromides can be regioselectively chlorinated one carbon away from the bromine (to give vic-bromochlorides) by treatment with PCls. Alkyl chlorides can be converted to vic-dichlorides by treatment with Mods. " Enhanced selectivity at a terminal position of w-alkanes has been achieved by absorbing the substrate onto a pentasil zeolite. In another regioselective chlorination, alkanesulfonamides... 

When the Cristol procedure was applied to the bridgehead acid (1), bicyclo[2.2.2]octane-l-caiboxylic acid, with bromine and mercuric oxide in carbon tetrachloride, the product was a mixture of the expected bromide (2) with an even larger proportion of the unexpected chloride (3). The chloride evidently arises by abstraction of chlorine from the solvent by an intermediate bridgehead radical. The pure bromide was obtained with use as solvent of either bromotrichloromethane or 1,2-dibromoethane. 

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