Dehydroannulenes annelated

The properties of annulenes annelated with a 675 ring system are of considerable interest with respect to the participation of benzenoid tt electrons in the macrocyclic Ti-electron system. In the field of dehydroannulenes, a wide variety of annelated derivatives, such as 313314 315316317318 , 319... 

The preparation of annelated tetrakisdehydro[18]annulenes 349 and 350 and the reference dehydroannulene 351 afforded further insight into the 7t-electron delocalization in annelated annulenes . When a dihydronaphthalene nucleus in 351 was replaced by naphthalene to form the annelated dehydroannulene 350, an appreciable suppression of diatropicity in 350 was observed. Further replacement of the dihydronaphthalene by naphthalene to give the dinaphtho-annelated derivative 349 resulted in a further suppression of the diatropicity in contrast to the increase of diamagnetic ring current in the case of transition from 342 to 340 and from 343 to 341. 

The Ti —To-value can be regarded as an approximate measure of -electron delocalization in annelated annulene rings. The above-mentioned results obtained on conformationally stable annelated acetylcne-cumulene dehydroannulenes seem to give the following conclusions ... 

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