Unusual formation of tricyclic annulenediones: diatropic cationic 10π-electron species in D₂SO₄

Abstract

Intramolecular oxidative coupling of 1 -(3-oxopent-1 -en-4-ynyl) -6-(1 -oxoprop-2-yny1)cyclohepta-1.3,5-triene 2 under the Glaser conditions unexpectedly afforded two tricyclic annulenediones. The unusual structures were determined b y X-ray crystallographic analysis of the compounds. These annulenediones are atropic in CDCI,, but exhibited diatropicity in CF,CO,D and D,SO, ascribable t o the formation of cationic 1 On-electron species.We have recently reported that in attempted cyclization of a series of diketones 1-9 carrying terminal acetylene groups under the Glaser conditions compounds 3, 5 and 7 gave, unexpectedly, the annulenediones 10, 11 and 12, respectively, containing a 1,4-dichIorobutatriene moiety. We showed that these annulenediones 10-12 exhibited strong diatropicity in D,SO, due to dicationic 14n-, 18n-and 22n-electron species respectively.Thus, the Glaser cyclization of compounds 1-9 succeeded when the side-chains at the 1 and 6 positions of the cycloheptatriene ring were of the same length except for the shortest and the longest members examined, 1 and 9, while 0 V O ~. 2, pp. 243-282. Structure Corporation (1 985).