The title annulenes have been synthesized and their 1H n.m.r. spectra indicate that the [28]- and [34]-annulenes as well as the lower-membered ones can sustain a ring current.
标题环已合成,其1 H nmr光谱表明[28]-和[34]-环以及低级环可以维持环电流。
Synthesis and Properties of a Bisdehydro[14]annuleno[<i>c</i>]furan and an Ortho-Annelated Tetrakisdehydro[14]annuleno[14]annulene
A bisdehydro[14]annuleno[c]furan and a tetrakisdehydro[14]annuleno[14]annulene have been synthesized; their properties and effects of annelation on annulene rings are discussed on the basis of 1H NMR and electronic spectra. Attempts to synthesize the related [14]annuleno[16]annuleno[14]annulene are also described.
10,12-Bisdehydro-3-isopropyl-9,14-dimethyl[14]- and -11,16-dimethyl[16]annuleno[a]azulene in which the conjugated 14- and 16-membered rings are fused to azulene ring, have been synthesized. It was found that the fusion of azulene ring suppresses the diatropicity of [4n+2], 14π-electron system to a smaller extent than benzene ring.
An [11][13]fulvalene derivative, 13-(4,9-methanocycloundeca-2,4,6,8,10-pentaenylidene)-4,9-dimethylcyclotrideca-1,3,9,11-tetraene-5,7-diyne, has been synthesized. Examination of 1H and 13C NMR spectra indicates that the compound shows no detectable ring-current effect in nonpolar solvents arising from 10π- and 14π-electron systems, which is verified by X-ray crystallographic structural analysis. In a polar solvent, [2H6]dimethyl sulfoxide, a small contribution of the dipolar resonance structure is suggested.