Annelated dehydroannulenes fused with azulene: synthesis and properties of tetradehydro[14]- and -[16]annuleno[a]azulenes

10,11,12,13-Tetradehydro-9,14-dimethyl[14]-, 10,11,12,13-tetradehydro-9,14-dimethyl[16]annuleno[a]azulene and their 3-isopropyl derivatives have been synthesized. The effect of annelation of a 10π-azulene ring onto the monocyclic [4n+ 2]π- and [4n]π-electron systems is discussed on the basis of 1H NMR and electronic spectra.