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The importance of indole derivatives as biologically active compounds is difficult to overestimate. Benzo[c,d]indoles are not an exception; for example, efficient inhibitors of thymidylate synthase were found among compounds of this series [1]. The present communication describes the synthesis of fused benzo[c,d]indole derivatives, 6H-pyrrolo[2,3,4-gh]perimidines IVa–IVc, from naphthalene-1,4,8-triamine (I) and 1,3,5-triazines IIa–IIc. We previously showed that 1,3,5-triazine in polyphosphoric acid (PPA) acts as efficient formylating and acylating agent [2–5], in particular toward naphthylamines [5]. Therefore, it may be expected that the use of 1,3,5-triazine should ensure convenient synthesis of pyrroloperimidines IVa–IVc. In fact, by heating triamine I with triazines IIa–IIc in PPA first at 80–90°C and then at 130–140°C we obtained the corresponding pyrroloperimidines IVa–IVc in 38–48% yield. The reaction is likely to involve intermediate formation of aminoperimidines IIIa–IIIc. Unlike the known procedure [6], the proposed method requires no preliminary preparation and acylation of perimidines. Furthermore, the key step in the known procedure [6] is the Schmidt reaction utilizing sodium azide in acid medium, and there exists a risk of evolution of toxic and explosive hydrazoic acid. The procedure proposed by us is free from the said disadvantage.

Condensed system (II) is obtained from aroylindoles (I) via Schmidt reaction and subsequent electrophilic amination of arenes using the sodium azide/PPA reagent system.

A method for the synthesis of 8-hydroxy-1,3,6-triazapyrenes (II) is given and a possible reaction mechanism is proposed.

The use of formic acid for the ring closure allows the synthesis of unsubstituted 1,3,6,8-tetraazapyrene (IIIa).

The peri-annulation of the pyrrole ring to perimidines is based on the reagent combination sodium azide/polyphosphoric acid and affords the hitherto unknown title compounds (III) in a one-pot fashion.

Quinolines are well known compounds for which a considerable number of synthetic methods have been developed.1 Nevertheless, no methods including the for mation of the N(1)—C(8a) and С(4)—C(4a) bonds were known in the literature. In the present work, we proposed such a method, which is based on the recently found re agent combination NaN3/polyphosphoric acid (PPA*). 3 We showed that the reactions of phenol (1a) and anisole (1b) with NaN3 in PPA at 55—60 °C for 3 h followed by addition of 1,3 dicarbonyl compound 2a,b and heating for additional 3 h at 120—130 °C afford quinolines 3a—с in yields of 31—42% (Scheme 1). The proposed mechanism of this transformation in cludes the formation of triazene 4 according to the mech anism analogous to that given in Ref. 3, the electrophilic attack of 4 by 1,3 dicarbonyl compound, cyclization of intermediate 5 to compound 6, and decomposition of the latter to yield azomethine 7, whose intramolecular alkyla tion affords quinolines 3 (Scheme 2). Thus, the consecutive reaction of sodium azide and a 1,3 dicarbonyl compound with an aromatic compound in PPA results in quinolines through the one pot reaction. In future, we intend to study to what extent this reaction is general with respect to aromatic and heteroaromatic com pounds.

Methods have been developed for the synthesis of 1,3,6,8-tetraazapyrene based on the reaction of 1,4,5,8-tetraaminonaphthalene with formic acid [1] and the synthesis of 2,7-dimethyl-1,3,6,8-tetraazapyrene based on the reaction of 6,7-diamino-2-methylperimidine with acetic anhydride [2]. These methods involve the use of not readily available starting reagents and are not general. In the present work, we propose a method for the synthesis of such compounds from available perimidine ketones 1a-c. Heating ketone 1a-c (1 mmol) and NaN3 (0.26 g, 4 mmol) in PPA (2-3 g) at 70-80°C for 1 h and then at 100-110°C for 4 h with monitoring by thin-layer chromatography leads to 1,3,6,8-tetraazapyrenes 4a-c in 31-44% yield. The PPA sample containing 87% P2O5 was prepared according to Uhlig [3]. This reaction involves the intermediate formation of amides 2a-c, whose amination using sodium azide in PPA, as previously described for perimidines [4, 5], leads to dihydro derivatives 3a-c, which are oxidized by atmospheric oxygen to give tetraazapyrenes 4a-c.

In previous work [1-4], we have developed a number of methods for the peri annelation of six-membered rings to give perimidines. In light of the high biological activity of a significant number of indole derivatives, we propose a method for the peri annelation of the pyrrole ring to perimidines. The reaction of ketones 1a-c (1 mmol) and NaN3 (0.07 g, 1.08 mmol) in PPA* (2-3 g) at 70-80°C for 1 h and then at 150-160°C for 4 h monitored by thin-layer chromatography leads to 1H-1,5,7-triazacyclopenta[c,d]phenalenes 3a-c in 36-48% yield. The reaction involves intermediante formation of amides 2a-c, which cam be isolated, for example 2a. The H NMR spectra were taken on a Bruker WP-200 spectrometer at 200 MHz in DMSO-d6 with TMS as the internal standard. The reaction course and purity of the products obtained were monitored on Silufol UV-254 plates with 1:1 ethyl acetate–ethanol as the eluent.

Method for the synthesis of 6,8-diaryl-1,3,7-triazapyrenes and 6,8-diaryl-1,2,3,7-tetraazapyrenes, based on the reaction of 2-R-1H-perimidines and 1H-naphtho[1,8-de][1,2,3]triazine with aromatic nitriles in polyphosphoric acid, has been elaborated.

The application of compound II in the role of formylating agent is well known [2]. In the classical version the reaction is carried out without catalyst or in the presence of Lewis acids. We demonstrated that under these conditions the perimidine formylation did not occur. Therefore another combination of reagents was used as formylating agent: 3-fold excess of 1,3,5-triazine II in 80% polyphosphoric acid (PPA) at 55–60°C. The yield of aldehydes IV under these conditions was 83–91%.

Several methods for the synthesis of 1,3-diazapyrene derivatives have been reported previously [1 5]. However, these methods suffer from poor yields and lack of general character. In the present communication we describe a procedure that is free from the above disadvantages. The procedure is based on the vinylformylation of heterocyclic compounds, which has been developed relatively recently [6]. We have found that perimidines Ia Ic react with 3-(Nmethyl-N-phenylamino)acrolein in dichloroethane in the presence of POCl3 to give the corresponding 1,3diazapyrenes IIIa IIIc in 42 56% yields.