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.Although theoretical calculations on monocyclic annulenes predicted that the limit of aromaticity of (4n + 2) x-electron systems would lie between 22-and 24-membered rings ,1 didehydro[26]annulene ,2 tetradehydro[26]annulene,3 and tetrahydro [30]annulene4 have proved to be diatropic. Also, the

JURO OJIMA, HIROSHI KAKUMI, KAZUTO KITATANI, KAZUYO WADA, EMIKO EJIRI, and TETSUYA NAKADA. Can. J. Chern. 63, 2885Chern. 63, (1985.For the purpose of preparing the ring-expanded analogue of anthracene, 1,2,4,5-tetrakis[(l E,3Z)-4-methylhexa-1,3-dien-5-ynyl]benzene, 8, and 1,2,4,5-tetrakis[(Z)-2(2-ethnylphenyl)etheny]benzene, 16, were oxidatively coupled; however, both of them afforded m-bridged derivatives, i.e., 1,3:4,6-bis[(l E,3Z,9Z,11 E)-4,9-dimethyldodeca-1,3,9,11-tetraene-5,7-diyne-l,12-diyllbenzene, 3, and 1,3:4,6-bis[(l E,11 E)-3,4:9,10-dibenzdodeca-l ,I 1-diene-5,7-diyne-l,12-diyllbenzene, 5.To ascertain the structures of 3 and 5, the related model compounds were also prepared.

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