| Popis: |
Earlier attempts to synthesize 1,2,3,8-tetrachlorocyclo-octatetraene 4 are described. A ca. 2:1 mixture of 1,2,3,8- and 1,2,3,4-tetrachlorocyclo-octatetraene was finally obtained by hydrolysis (using 96% trifluoroacetic acid) of the ketal 15 followed by thermal decarbonylation of the product. Reaction of the mixture of cyclo-octatetraenes with bromine gave the (separable) dibromo-derivatives 17 and 18. On attempted debromination with zinc, the dibromodiene 17 formed the benzocyclobutadiene dimer 12, together with the benzobiphenylene 13; these compounds were also produced directly from the cyclo-octatetraene mixture by the action of zinc. In contrast, similar treatment of the dibromodiene 18 led to the E-bromostyrene 22. The mixture of cyclo-octatetraenes reacted with maleic anhydride to give the adduct 27, whereas with acenaphthylene the adduct 28 was obtained. |
