The Chemistry of Heterasumanenes

Our studies on the synthesis of heterasumanenes, where benzylic carbon atoms of the sumanene are replaced by heteroatom functionalities, are summarized. Starting from triphenylene, repetitive lithiation at a bay position followed by introduction of silylene or germylene units provided the first trisila- and trigermasumanenes with no substituents on the skeletal carbon atoms. The synthesis of a trisilasumanene bearing six butoxy groups on the skeletal carbon atoms was also accomplished by our original sila-Friedel-Crafts reaction. A heterasumanene bearing three different heteroatom functionalities was also prepared from triphenylenothiophene by a sequential lithiation method, even though protecting groups were necessary to prevent lithiation at the α-carbon atoms of the dibenzothiophene unit. Structural analysis and optical properties of the novel heterasumanenes are also described.