SYNTHESIS AND PROPERTIES OF TETRAMETHYLOCTADEHYDRODIHYDRO-[26]-, TETRAMETHYLOCTADEHYDRODIHYDRO-[28]-ANNULENEDIONE, TETRAMETHYLOCTADEHYDRODIHYDRO-[30]-ANNULENEDIONE, TETRAMETHYLOCTADEHYDRODIHYDRO-[32]-ANNULENEDIONE AND TETRAMETHYLOCTADEHYDRODIHYDRO[34]-ANNULENEDIONE

Title annulenediones 5-9 were synthesized by intermolecular oxidative coupling of 6-methylocta-3,5-dien-7-yn-2-one 13 or its vinylogous keto nes 14 and 15 to afford the diones 17-21 and then by an aldol condensa tion of these diones 17-21 with (Z)-3-methylpent-2-en-4-ynal 10, follo wed by intramolecular oxidative coupling of the resulting acyclic diac etylenes 22-26. The properties of the title compounds 5-9 are discusse d on the basis of H-1 NMR and electronic spectra.