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The hitherto unknown syn and anti isomers of benzotris(norbornadiene) 7, the only molecules that include both features known to lead to bond length alternation in benzenes, i.e. bicyclic ring strain and π–π interaction, have been synthesized from 2,3-dibromonorbornadiene using butyllithium and copper(I) iodide.
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Durr et al. (1996) studied this question.
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