Studies on Cage Compounds. Synthesis of 8,11-Diazenediyl-4,4-Dimethoxy-2,3,5,6-Tetrachloropentacyclo[5.4.0.02,5.03,10.05,9]Undecane

The title compound ( 7 ) was synthesized in six steps from 1,8,9,10-tetrachloro-11,11-dimethoxy-endo-tricyclo6.2.1.0^2,7]undeca-4,9-diene-3,6-dione ( 4 ) in an overall yield of 36%. The key intermediate, 1,8,9,10-tetrachloro-11,11-dimethoxy-endo-tricyclo-6.2.1.0^2,7]undeca-3,5,9-triene ( 12 ), obtained from 4 by reduction, mesylation and then 1,4-elimination, was allowed to react with diethyl azodicarboxylate to afford the Diels-Alder adduct 16 . Photochemical closure of 16 , followed by hydrolysis and decarboxylation, gave the title compound. The title compound failed to give either the homopentaprismanone derivative 3 or the diene 9 by the photochemical or thermal elimination of molecular nitrogen.