Acylation of Cyclooctatetraene Dianion and the Chemistry of Its Products

Cyclooctatetraene dianion (I) reacts as a 1,2and a 1 ,4-dicarbanionic reagent with various acyl halides. Thus I and acetyl chloride give 3,5,7,9-dodecatetraene-2,1l-dione (111), syn-9-acetoxy-9-methylbicyclo[4.2.1]nonatriene (V), syn-9-hydroxy-9-methylbicyclo[4.2.l]nonatriene (IV), and syn-9-acetoxy-9-methylbicyclo[6.1 .O]nonatriene (VI). Benzoyl chloride and I yield truns,cis,cis,trans-l ,lO-dipheny1-2,4,6,8-decatetraene-l ,IO-dione (XIV) and syn-9-benzoyloxy-9-phenylbicyclo[4.2.l]nonatriene (XV); similar products (XIX and XX) are obtained from p-bromobenzoyl chloride and I. The lactone XXV of 9-(2-carboxyphenyl)-9-hydroxybicyclo[6.l.O]nonatriene is obtained from I and phthaloyl chloride. The structures of these products are proven by combination of chemical degradation and synthesis. Pyrolysis of the bicyclo[4.2.l]nonatrienes (V and XV) gives 2-substituted indenes; the bicyclo[6.1 .O]nonatriene (VI) yields 3-methylindene. The mechanisms of these pyrolyses are discussed. ne of the important developments of modern 0 structural theory has been the demonstration of the existenceZatb and aromatic c h a r a ~ t e r ~ ~ , ~ of the cyclooctatetraene dianion (I). That I is planar and