4.9- diazapyrenes

Coverage of perimidine chemistry can be found in two review articles <1981RCR816, 1995AQ151>, while benzo[g/5]perimidine chemistry is discussed in a review of diazapyrenes <2003CHE1417>. 

Pyrimidine 1 is the lUPAC accepted name for 1,3-diazabenzene, while quinazoline 2 is the accepted name for benzo[r lpyrimidine or 1,3-diazanaphthalene. Perimidine 3 is the lUPAC accepted name for l//-benzo[r/ ]quinazoline or H -naphtho[l,8-r/i ]pyrimidine, while benzo. 4]perimidine 4 is also known as 1,3-diazapyrene. 

A six-membered ring is formed in the reduction of 2-nitrobiphenyl-2 -carboxylic acid68 or 6,6 -dinitrobiphenyl-2,2 -dicarboxylic acid.69 In the former case a phenanthridine is formed, in the latter a 4,9-diazapyrene. Similarly, a seven-membered ring is obtained when 2-nitro-2 -isothiocyano-biphenyl (15) is reduced in acidic solution with the formation of 6-mercapto-dibenzo[d/]-l,3-diazepine 3-oxide (16)70 [Eq. (28)]. 

The question of whether 10b, 1 Oc-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. 

---