SYNTHESES AND PROPERTIES OF METHANE-BRIDGED DICHLORODIDEHYDRO-[16]-ANNULENEDIONE, DICHLORODIDEHYDRO-[20]-ANNULENEDIONE AND DICHLORODIDEHYDRO-[24]-ANNULENEDIONE

Bisethynylation of the vinylogous dialdehydes of cyclohepta-1.3,5-trie ne-1,6-dicarbaldehyde with ethynylmagnesium bromide followed by oxidat ion of the resulted diols afforded the diacetylenic diketones. Intramo lecular oxidative coupling of these diketones under the Glaser conditi ons unexpectedly afforded three annulenediones with a 1,4-dichlorobuta triene moiety. The unusual structures were confirmed by X-ray crystall ographic analysis of ichloro-11.12-didehydro-1,6methano[16]annulene-9, 1 4-dione. These annulenediones exhibited strong diatropicity in D2SO4 due to the dicationic 14 pi-, 18 pi- and 22 pi-electron species and t heir diatropicities were shown to increase with increasing ring size.