title: Acid-catalyzed transannular cyclization of 3aH-cyclopentene[8]annulene-1,4-(5H,9aH)-diones and some proposed mechanisms.
abstract: Bicyclic 3aH-cyclopentene[8]annulene-1,4-(5H,9aH)-diones underwent three types of acid-induced transannular 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-substituent permitted the Michael reaction for all acids used to give tricyclic diones by the activation of cyclopentenone carbonyl group. However, the Ph-substituent inhibited the Michael reaction for BF3 and MeSO3H but allowed the [3 + 2] cycloaddition and Friedel-Crafts reaction for CF3SO3H depending on the position of annulenone substituent. These CF3SO3H reactions exhibited the following novel rearrangements, affording 2-naphthalenone and 7-acenaphthylene derivatives, respectively. The factors that control the reaction mode of these transannular cyclizations were discussed in view of the constraint twist-boat conformation of [8]annulenone ring as well as the ring substituent effects on the intramolecular cyclization. In addition, these [8]annulenone rings were found to easily undergo the intramolecular [2 + 2] photocyclization to provide the tetracyclic cage compounds which exhibited the facile cycloreversion under the influence of acid.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Yamada-oka, Suita, Osaka 565-0871, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Koizumi
authors.forename: Kenji
authors.initials: K
authors.lastname: Harada
authors.forename: Haruyasu
authors.initials: H
authors.lastname: Asahara
authors.forename: Eiko
authors.initials: E
authors.lastname: Mochizuki
authors.forename: Ken
authors.initials: K
authors.lastname: Kokubo
authors.forename: Takumi
authors.initials: T
authors.lastname: Oshima
mesh_terms: D000143:Acids / Q000737:chemistry*; D001952:Bridged-Ring Compounds / Q000138:chemical synthesis*; D002384:Catalysis; D003500:Cyclization; D003517:Cyclopentanes / Q000737:chemistry*; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry*
chemical_list: D000143:Acids; D001952:Bridged-Ring Compounds; D003517:Cyclopentanes; D011084:Polycyclic Aromatic Hydrocarbons