Reactions of some cyclopropanes activated by a spiro-linked fluorene. Importance of electronic matching of a reacting partner in thermal cycloaddition with TCNE and ring-opening dehydrogenation with DDQ
group were readily dehydrogenated by DDQ, but not by chloranil, to give a butadiene derivative, which reacted further with DDQ to afford 7-(o,o′-biphenylene)-3,4-dichloro-1,6-dicyano-9-alkylbicyclo[4.4.0]deca-3,8-diene-2,4-dione. In contrast, methylcyclopropanes substituted merely by two phenyl groups were reluctant to undergo the dehydrogenation.