| Abstract
| - Bicyclic 3aH-cyclopentene[8]annulene-1,4-(5H,9aH)-diones underwent three types of acid-inducedtransannular reactions, Michael cyclization, [3 + 2] cycloaddition, and Friedel−Crafts ipso-alkylation, depending on the cyclopentenone ring substituent (Me or Ph) and the position of [8]annulenone substituent as well as the nature of acids (BF3, MeSO3H, CF3SO3H). The Me-substituentpermitted the Michael reaction for all acids used to give tricyclic diones by the activation ofcyclopentenone carbonyl group. However, the Ph-substituent inhibited the Michael reaction forBF3 and MeSO3H but allowed the [3 + 2] cycloaddition and Friedel−Crafts reaction for CF3SO3Hdepending on the position of annulenone substituent. These CF3SO3H reactions exhibited thefollowing novel rearrangements, affording 2-naphthalenone and 7-acenaphthylene derivatives,respectively. The factors that control the reaction mode of these transannular cyclizations werediscussed in view of the constraint twist-boat conformation of [8]annulenone ring as well as thering substituent effects on the intramolecular cyclization. In addition, these [8]annulenone ringswere found to easily undergo the intramolecular [2 + 2] photocyclization to provide the tetracycliccage compounds which exhibited the facile cycloreversion under the influence of acid.
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