Synthesis of compounds related to cyclohepta[def]fluorene

Abstract

Two syntheses of cyclohepta [def]fluoren-8(4H)-one (XIX) are described; one involves ring enlargement of 4H-cyclopenta [def]phenanthrene (VIII) and the other cyclisation of fluorene-4-propioni acid (XXVII). The 4H-cyclophepta[def]fluorenyl salts (XXIV) and (XXX) are not converted into cyclohepta[def]fluorene by reaction with pyridine or triethylamine and this is in accord with the predicted abnormally high nucleophilic reactivity of the 4-position of cyclohepta[def]fluorene. The heptafulvene (XLI) and the tropone (XIX) are evidently considerably more stable than their [def]fluorene tautomers (XLII) and (XX); this result is consistent with the calculated low π-electron energy of the cyclohepta[def]fluorene system.