FACILE FORMATION OF DIHYDROACEPENTALENEDIIDE FROM CENTRO-SUBSTITUTED TRIBENZOTRIQUINACENES WITH C-C BOND-CLEAVAGE

Tribenzodihydroacepentalenediide 5, a potential precursor for tribenzo acepentalene 6, can be prepared in good yields from the easily accessi ble centro-substituted tribenzotriquinacenes 7a-c by treatment with an excess of n-butyl lithium/potassium t-pentoxide in the presence of te tramethylethylene diamine (TMEDA). The dimer 16 of tribenzodihydroacep entalene 15, thus obtained after hydrolysis of 5 in up to 85% yield fr om readily accessible 7a, undergoes [2+2]-cyclo-reversion at 220-degre es-C, and 15 is efficiently trapped in [2+4]-cycloadditions with non-v olatile dienes like tetracyclone and anthracene to give structurally i nteresting polycycles 17 and 18, respectively.