The 1,6-bis(2,5-dimethoxyphenyl)hexa-2,4-diynes 4a-c were hexa-2,4-diyne unit is observed, with the 1,6-diphenyl substituents arranged in a coplanar orientation. According to obtained from the corresponding 2,5-dimethoxybenzenes 1 by bromination followed by a copper-catalyzed Grignard the crystal structure data obtained, irradiation of diynes 4a and 4b afforded the deeply-colored, highly-ordered polymers reaction with 3-bromoprop-1-yne. Catalyzed coupling of the resulting 3-(2,5-dimethoxyphenyl)prop-1-ynes 3 under Hay 5a and 5b under topochemical control. Oxidation of 4a and 4b with cerium(IV) ammonium nitrate gave the conditions gave the hexa-2,4-diynes 4a-c in good yields. The molecular structures of the diynes 4a and 4b were corresponding 1,6-bis(2,5-dimethoxyphenyl)hexa-2,4-diyne-1,6-diones 6a and 6b. determined by X-ray diffraction analysis. In each crystal structure, an unusual 1,6-synperiplanar conformation of the of magnesium turnings and then 3-bromoprop-1-yne in the [a] Organisch-Chemisches Institut der UniversitΓ€t Heidelberg, state irradiation of conjugated diynes. [1,17Οͺ20] Because of Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany the known insolubility of poly(but-1-ene-3-ynylene), only