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Perimidones, 2,3-dihydroperimidines [2, 3] and perimidines [4] are known to be easily acylated at the 6(7)-(para) or 4(9)-(ortho) positions. Carboxylic acids in polyphosphoric acid were used as the acylating agents. For perimidones, acyl chlorides in the presence of anhydrous AICI3 were used [5]. Therefore, we expected that formylation of these compounds might proceed just as easily. The present work tests that hypothesis.We found that 1,3-dialkylperimidones (Ia and Ib) undergo the Vilsmeier reaction (POC13-DMF) at 60-80~ to form the perimidon-6-carboxaldehydes Ha, b in 80-85% yield. It seemed interesting to determine if the monoaldehydes could be further formylated, keeping in mind that perimidones readily undergo diacylation [3]. Heating IIa with an excess of Vilsmeier reagent (60-80~ 5.5 h) led to formation of resin. The only product in about 20% yield was 1,3-dimethylperimidon-4-carboxaldehyde (III), which was somewhat unexpectedly isolated. A similar isomerization was previously observed for 6-acylperimidines with an unsubstituted N-H group [4]. It was proposed that this isomerization is driven by the formation in 9-acyl derivatives of a strong intramolecular hydrogen bond (IHB). Since this is not a factor for aldehyde III, the migration of the formyl group to the more sterically hindered ortho position is apparently due to some other reason. It is noteworthy that aldehyde IIa is completely destroyed by heating with polyphosphoric acid for -30 min, forming a dark green crystalline product. Judging from the PMR spectrum, the product is a complex mixture of oligomers. The tendency to oligomerize in acidic medium probably explains the relatively low yield oflII. Formylation of 1,3-dimethyl-2,3-dihydroperimidine (IV) is more complicated and significantly less regioselective. The reaction goes slowly even at -20-(-30)~ However, it is better conducted at room temperature.

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Published data on methods for the synthesis of mono-, di-, tri-, and tetraazapyrenes are reviewed.It is theoretically possible to envisage about 300 isomeric aza-and polyazapyrenes with the nitrogen atoms at various positions around the periphery of the pyrene ring and also many mono-and dications with a bridging positively charged nitrogen atom. At present, according to our data, only a small number of these aromatic nitrogen heterocycles have been synthesized.The attention paid to azapyrenes is due both to theoretical aspects (aromaticity, thermodynamic stability, the mechanism of electrophilic and nucleophilic substitution, the stability of the radical-ions, etc.) and to the results of applied studies. In particular, the change of the biological activity with the inclusion of nitrogen atoms in the pyrene ring, i.e., the transition from pyrene to its aza and polyaza analogs, is of undoubted interest. Thus, whereas the monoazapyrenes found in natural subjects [1-4] exhibit mutagenic and carcinogenic activity [5] the derivatives of the most investigated 4(9)-and 2,7-diazapyrenes exhibit analgesic [6] and antiviral and antibacterial [4] activity, and also anticancer activity [8][9][10]. The mechanism of such activity is usually attributed to their known ability to act as intercalators [11][12][13][14][15][16][17][18][19][20]. Polyazapyrenes are actively used in supramolecular chemistry for the construction of molecular devices [21], compounds with topological bonding [22], molecules of the "host-guest" type [23], and macrocomplexes with the cations of transitional metals [24,25].In this review the generally accepted substitutive aza nomenclature [26] is used for these compounds, although other names were used in the earlier papers.

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The use of 1,3,5-triazines 2 as formylating agents in the presence of a Lewis acid has been reported [1]. The use of substituted 1,3,5-triazines as acylating agent was not known. We have shown that formylation of perimidine 1 does not occur under these conditions. Formylation has been successfully carried out with a threefold excess of 1,3,5-triazine 2 in 80% PPA (4 g per mmol of perimidine) at 55-60°C for 1 h. The yield of perimidine-6(7) carbaldehyde (3a) was 91% under these conditions. The compound was separated by pouring the reaction mixture into water with subsequent basification of the solution with ammonia and extraction with ethyl acetate. Compound 3a was previously successfully obtained in a yield of less than 10% by the Vilsmeier reaction [2]. We have shown that by using substituted 1,3,5-triazine ketones 3b,c can be obtained. In this case the reaction time is 2.5 h at a temperature of 80 and 110°C respectively. + 1 2a-c PPA 3a-c 2, 3 a R = H, b R = Me, c R = Ph Perimidine-6(7)-carbaldehyde (3a). Yield 91%; mp 212-214°C ( from acetic acid) (mp 212-214°C [2]). A mixed melting point with a known sample gave no depression of the melting point. The 1 H NMR spectrum coincided with that cited in [2]. 6(7)-Acetylperimidine (3b). Yield 78%; mp 221-222°C (from aqueous ethanol) (mp 221-222°C [3]). A mixed melting point with a known sample gave no depression of the melting point.__________________________________________________________________________________________

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