Bicyclo hexacosane

Heterocyclic systems in which atropoisomerism is possible are known, but now the first syntheses of similar carbocyclic systems are reported. With bicyclo-[2,2,2]octane it is sterically impossible for the bridgehead carbon to invert and place the bridgehead hydrogen within the interior of the skeleton, but with much larger ring systems this inversion becomes possible so that with bicyclo-[8,8,8]hexacosane ° three atropoisomers, (200)—(202), are possible. The synthesis of (201) and (202) is shown in Scheme 21. The cis- and frans-isomers... 

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