Fused Polycyclic and peri-Condensed Benzenoid Systems

Fused Polycyclic and peri-Condensed Benzenoid Systems 

With the exception of fluoranthene, which was synthetically isolated in the 1930s by von Braun and Anton [71], and decacydene, a key signature of 1950s chemistry was the rapid expansion of conjugated, fused systems with five-membered rings. 

The noteworthy investigators of these systems include Clar, Campbell, Lang, and Aitken. The majority of systems developed were benzo-derviatives of fluoranthene, benzofluoranthene 81 (Fig. 1.6b), and phenylenefluoranthene 82 [la, 72]. Some of the more novel systems included an additional fused seven-membered ring. In 1956, Boekelheide and coworkers produced acepleiadylene 83, unique in structure due to fusion of three ring sizes [73], Starting from previously isolated diketone 84, 

The 1950s and 1960s also saw work on a number of linearly-annelated benze-noid derivatives of the highly reactive hexa- and heptacene as well as the first octa-cene derivative. One notable structural motif present in all of the analogs is a pyr- 

The largest fused benzenoid systems developed prior to 1970 were based on perylene, peropyrene 93, terrylene 94, coronene, and bisanthene (Fig. 1.8). Also responsible for terrylene, Clar and coworkers produced three additional benzenoid derivatives as well as circumanthrene 95, isolated from two-fold condensation of tetracene derivatives in 1956 [laj. Halleux and coworkers obtained tetrabenzobisan-thene 96 from Zn-dust dimerization of dibenzoperinaphthone [79]. Synthesized by Clar in the same year [laj, hexabenzocoronene 97 was produced by Halleux and coworkers in 1958 from a NaCl-ZnCl melt of hexaphenylbenzene [79j. 

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