Tetrabenzo annulene

The first benzoannulenes were prepared in effect purely as examples of annulenes, the presence of the benzene rings serving to make the synthesi.s easier and/or in the hope that they would serve to make the final product more stable and handleable. For example, before any unannelated annulene had been prepared the tetrabenzo-annulenes (LvlII) [249] and (LIX) [250] had been described. Both... 

Thermal bond transposition has been utilized successfully in the synthesis of a number of relatively heat-insensitive families of heteroannulenes, such as the triheteronin frame (20) constructed thermally from the tetracyclic valence tautomer and the tetrabenzo heteronins (18) obtained by thermal bond transposition of their spirostructured valence tautomers (113). Similarly, thermally induced bridge extrusion (C02) has been utilized as a means of preparing dihydrobenzazonine (112) (the direct photoprogenitor of aza[13]annulene 36a) from cycloadducts (104) (73TL3805). 

Boese, R Matzger, A.J Volhardt, K.P.C. Synthesis, crystal structure, and explosive decomposition of 1,2 5,6 11,12 15,16-tetrabenzo-3,7,9,13,17,19-hexa-dehydro[20]annulene formation of onion- and tube-like closed-shell carbon particles. J. Am. Chem. Soc. 1997, 119, 2052-2053. 

Benzo-fused [8]annulenes containing twisted % systems have also received great attention lately (Figure 5.5). In this section, we will review the synthesis and properties of some bent jt-conjugated systems comprised of benzo-fused[8]annulenes, excluding those with COT rings coordinated to metals. Tetrabenzo[a,c,e, ]cyclooctene (tetraphenylene) and its derivatives will be discussed in the next section. 

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