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