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Synthetic strategy directed towards the synthesis of bicyclo[3.3.0]octa-3,5,8-triene-2,7-dione

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2004
Atalar, Taner
Although the chemistry of benzenoid and nonbenzenoid quinones have been the subject of extensive theoretical and experimental studies, the extent of our present understanding regarding the geometries and stabilities of quinones of pentalene is meager. After studying the existence of cyclopentadienone and its reactivity as a diene and dienophile in the literature, the study of some related species, particularly the ones with fully unsaturated pentalenic structures were started. In this thesis, the elusive compound bicyclo[3.3.0]octa-3,5,8-triene-2,7-dione was tried to synthesize by using the synthetic strategy which was developed by us. We used cycloheptatriene as the starting material. The bicyclic endoperoxiedes mixture obtained by the photooxygenation of cycloheptatriene was v treated with triethylamine to give tropone in high yield. Selective reduction of tropone afforded cyclohepta-3,5-dione which was converted by the way of photochemistry to the bicyclo[3.2.0]hept-6-en-3-one. After protection of the carbonyl group, dibromocarbene was added to the double bond to give desired bicyclic compound with pentalene skeleton. Substitution of the allylic bromide with hydroxyl group followed by PCC oxidation resulted in the formation of a diketone. All efforts to convert this diketone into fully conjugated system failed.