10b,10c-Diazapyrenes

The question of whether 10b,10c-diazapyrene (309) is capable of a finite existence has been the subject of theoretical considerations. According to HMO calculations it was suggested to be the stable valence tautomer compared with (310). The pyridinophane (310) has been prepared but no indication of valence tautomerization to give (309) was found (70CC1558). The synthesis of this compound remains a challenge. 

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