Kaori Asano

Unusual formation of a methano-bridged didehydro[20]annulenedione. A highly diatropic, dicationic 18π-electron species in D2SO4

An intramolecular coupling of 1,6-bis(5-oxohepta-1,3-dien-6-ynyl)cyclohepta-1,3,5-triene under Glaser conditions affords 12,15-dichloro-13,14-didehydro-1,6-methano[20]annulene-11,16-dione, which exhibits strong diatropicity in D2SO4, suggesting the formation of the highly delocalized dicationic species.

Synthesis and properties of methano-bridged tetradehydro-[20]-, -[24]-, -[26]-, -[28]-, -[30]- and -[32]-annulenediones

The title annulenediones 4–9 have been synthesized by first an aldol condensation of cyclohepta1,3,5-triene-1,6-dicarbaldehyde 10 or its vinylogous dialdehydes 11–14 with acetone to afford the dimethyl diketones 16–20 and then by a second aldol condensation of 1,6-diacetylcyclohepta1,3,5-triene 15 or the dimethyl diketones 16–20 with (Z)-3-methylpent-2-en-4-ynal 21, followed by intramolecular oxidative coupling of the resulting acyclic diacetylenes. The properties of the title compounds are discussed on the basis of 1H NMR and electronic spectra as well as cyclic voltammetry.

Synthesis and properties of dimethano-bridged tetradehydro[21]-, -[23]- and -[25]annulenones

Syntheses of 7,8,9,10-tetradehydro-1,6:11,16-dimethano[21]annulen-19-one 11, 7,8,9,10-tetradehydro-18-methyl-1,6:11,16-dimethano[21]annulen-19-one 12, 7,8,9,10-tetradehydro-1,6:11,16-dimethano[23]annulen-19-one 13 and 7,8,9,10-tetradehydro-1,6:11,16-dimethano[25]annulen-21-one 14 are described. The influence of an introduction of two methano-bridges upon the structure and tropicity of the tetradehydro-[21]-, -[23]- and -[25]annulenone ring systems is discussed in view of the 1H NMR and electronic spectra of these annulenones as well as those of the corresponding monocyclic annulenones.

Synthesis and properties of a new methano-bridged tetradehydro[22]annulenedione

The title annulenedione 8 was synthesized starting from 1-acetyl-6-(3-oxobut-1-enyl)cyclohepta-1,3,5-triene 25 by aldol condensation with (Z)-3-methylpent-2-en-4-ynal 26 to afford the dione 27 and then by another aldol condensation of the dione 27 with the aldehyde 26, followed by intramolecular oxidative coupling of the resulting acyclic diacetylene 28. Examination of the 1H NMR spectra indicated that compound 8 is paratropic in acidic media.

Unusual formation of tricyclic annulenediones: diatropic cationic 10π-electron species in D2SO4

Intramolecular oxidative coupling of 1-(3-oxopent-1-en-4-ynyl)-6-(1-oxoprop-2-ynyl)cyclohepta-1,3,5-triene 2 under the Glaser conditions unexpectedly afforded two tricyclic annulenediones. The unusual structures were determined by X-ray crystallographic analysis of the compounds. These annulenediones are atropic in CDCl3, but exhibited diatropicity in CF3CO2D and D2SO4 ascribable to the formation of cationic 10π-electron species.

Syntheses and properties of methano-bridged dichlorodidehydro-[16]-, -[20]-and-[24]-annulenediones

Bisethynylation of the vinylogous dialdehydes of cyclohepta-1,3,5-triene-1,6-dicarbaldehyde with ethynylmagnesium bromide followed by oxidation of the resulted diols afforded the diacetylenic diketones. Intramolecular oxidative coupling of these diketones under the Glaser conditions unexpectedly afforded three annulenediones with a 1,4-dichlorobutatriene moiety. The unusual structures were confirmed by X-ray crystallographic analysis of 10,13-dichloro-11,12-didehydro-1,6-methano[16]annulene-9,14-dione. These annulenediones exhibited strong diatropicity in D2SO4 due to the dicationic 14π-, 18π- and 22π-electron species and their diatropicities were shown to increase with increasing ring size.