Annulenes cycloaromatization

FIGURE 35. Polymerization schemes of octatetrayne derivatives and cycloaromatization of 1,6-didehydro[10]annulene (98). Reprinted with permission from Reference 53. Copyright (1994) American Chemical Society... 

The importance of this cycloaromatization in modern aromatic chemistry only became obvious when it was realized that it constitutes an optimal route to bowl-shaped aromatics and fullerene partial structures [9, 18, 19]. The key experiment, Scott s synthesis of cor-annulene (40) from 7,10-diethynylfluoranthene (37) [20], was quickly adapted to more extended systems, the examples 38 —> 41 [21] and 39 —> 42 [22] in Scheme 10 being just two of many ... 

It was found that soUd-state polymerization of these monomers always proceeds by 1,4-addition. Furthermore, polydiacetylene 96 could be thermally reacted and the structure of the final polymer was proposed to be that of the ladder polymer 97 where the repeating unit is l,6-didehydro[10]annulene (98), i.e. two conjugated polydiacetylenes. However, the annulene 98 is expected to be unstable. In fact, its cycloaromatization reaction to the... 

Myers has also studied the cycloaromatization of the related aromatic hydrocarbon l,6-didehydro[10]annulene (65, Scheme 7-19), demonstrating that the reaction has a half-life of 25 min at -51 C and making it one of the most rapid diradical-forming reactions known [138, 139]. 

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