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The synthesis of 8,13-dimethyl-2,9,11-trisdehydro[16]annulene-1,4-dione. The protonation of a [4n]annulenedione to a strongly diatropic dication

✍ Scribed by Luciano Lombardo; Franz Sondheimer

Publisher
Elsevier Science
Year
1976
Tongue
French
Weight
219 KB
Volume
17
Category
Article
ISSN
0040-4039

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✦ Synopsis

Several macrocyclic vinylogues of pbenzoquinone (11C61annulene-l,~dione"l containing (4&+2)membered rings have recently been synthesized (2 = 3 2; n = 4 394) 5 . C-n the other hrd, in the C4nlannulenedione series, the only members known until now were cyclobutenedione (1) end derivatives 7 (g = 11, as well as 2,5,7-cyclooctatriene-1,4-dione (2) (& = 2).8 We now describe a remarkably simple synthesis of 8,lj-dimethyl-2,~,11-trisdehydro~16~annulene-l,~dione (j_),9 the first macrocyclic c4nlannulenedione derivative (2 = 4). This substance proved to be appreciably 0 0 Yf -1 0 -'0" 0 / 1 0 0 c diatropic ("aromatic"), indicating the contribution of canonical forms such as &.

More importantly, treatment of the dione j_with D,SO4 has been found to eve rise to the stron@,y diatropic dication &, a type of transformation which has not hitherto been observed in this series of diketones.

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