H. Higuchi et al., ANNELATED DEHYDROANNULENES FUSED WITH AZULENE - SYNTHESIS AND PROPERTIES OF TETRADEHYDRO[14]ANNULENO[A]AZULENE AND TETRADEHYDRO[16]ANNULENO[A]AZULENE, Journal of the Chemical Society. Perkin transactions. I, (9), 1994, pp. 1167-1177
10,11,12,13-Tetradehydro-9,14-dimethyl[14]-, 3-tetradehydro-9,14-dimet
hyl[16]annuleno[a]azulene and their 3-isopropyl derivatives have been
synthesized. The effect of annelation of a 10 pi-azulene ring onto the
monocyclic [4n + 2]pi- and [4n]pi-electron systems is discussed on th
e basis of H-1 NMR and electronic spectra.