Efficient pharmaceutical compounds, organic luminophors, and dyes have been found among the few azapyrenes synthesized [for example, 1, 2]. On the other hand, a considerable fraction of azapyrenes remains difficult to prepare and, thus, these compounds have not been studied extensively.We have developed a method for the synthesis of 1,3,6,8-tetraazapyrenes using perimidine ketones [3]. Disadvantages of this method are the need initially to introduce a carbonyl group into the perimidines and the impossibility of fusion of a pyrimidine ring without a substituent at the carbon atom. A method eliminating the latter disadvantage involves the reaction of 1,4,5,8-tetraaminonaphthalene with formic acid [4] and permits the preparation of only 1,3,6,8-tetraazapyrene itself.In the present work, we propose a synthetic method involving a one-pot sequence of nitration of perimidines 1a,b, reduction of dinitro derivatives 3a,b, and heterocyclization. NH N R NH N R NO 2 NO 2 N N R N N NH N R NO 2 NO 2 1a,b 2a,b 1) NaNO 2 /HCOOH 4a,b 2) HNO 3 /HCOOH + 3a,b Zn/HCOOH  1-4 a R = H; b R = MeThe 1 H NMR spectra were taken on a Bruker WP-200 spectrometer at 200 MHz in DMSO-d 6 with TMS as internal standard. The course of the reactions and purity of the products were monitored by thin-layer chromatography on Silufol UV-254 plates using 1:1 ethyl acetate-ethanol as the eluent.

Nitro compounds are important intermediates in the synthesis of differently functionalized arenes. We have previously proposed a method for the nitration of perimidines using nitric acid (d 1.5) in acetic acid [1]. The product yields for mononitration at a peri position (the 6(7)-nitroperimidines 2 are 8% for perimidine 1a and 46% for the 2-methylperimidine (1b). We have proposed that the low yield is linked to an incorrect choice of nitrating conditions. It was found that refluxing the perimidines 1a-c (1 mmol) with NH 4 NO 3 (0.12 g, 1.5 mmol), and glacial acetic acid (25 g) for 5-10 min (TLC monitoring), cooling, neutralization of the reaction mixture to pH ~ 8 with sodium carbonate solution, and filtration of the precipitate obtained gave the 6(7)-nitroperimidines 2a-c in 76-83% yields. NH N R NH N R NO 2 NH N R NH 2 1a-c 2a-c AcOH NH 4 NO 3 3a-c Zn AcOH 1-3 a R = H, b R = Me, c R = PhTreatment of the reaction mixture before neutralization with zinc powder (0.32 g, 5 mmol), refluxing for 30 min (TLC monitoring), filtration to remove the excess zinc, neutralization of the mother liquor, and filtration gave the corresponding 6(7)-aminoperimidines 3a-c in 62-69% yields.

One-Pot Synthesis of 1,3,6,8-Tetraazapyrenes. -The use of formic acid for the ring closure allows the synthesis of unsubstituted 1, 3,6,. The reaction proceeds via 6,7-dinitroperimidines; the corresponding 6,9-dinitro derivatives can be isolated as side products after step 2 (yields 29% and 25%, respectively).