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A highly efficient protocol for acid-mediated peri-annulation of perimidines with pyrimidines was developed. Pyrimidines, used as surrogates for 1,3-dicarbonyl compounds allow for furnishing benzo[gh]perimidines, including hardly available analogs, non-substituted, or mono-substituted at C-6, C-8. Limitations of reactions employing 5-bromopyrimidines are investigated.

Several highly efficient one-pot synthetic protocols were developed, enabling polyphosphoric acid-activated nitroalkanes to act as electrophiles in reactions with aminonapthalenes. The featured methods allow for the single step assembly of polyheterocyclic aromatic derivatives of 6H-pyrrolo[2,3,4-gh]perimidine scaffold in high yields.

A route towards pyrrolo[2,1-a]isoquinolines through a 3CR of 1-aroyl dihydroisoquinolines, activated alkynes and alcohols has been developed.

This novel one-pot protocol allows the conversion of indoles into indolylacetonitriles via electrophilic aromatic alkylation with nitroalkenes and subsequent reductive dehydration.

PPA-activated nitroalkanes are employed in the design of a one-pot cascade transformation involving metal-free and oxidant-free direct ortho-C–H functionalization, followed by Beckman rearrangement and intramolecular cyclocondensation to produce benzoxazoles and benzobisoxazoles directly from easily available phenols.

The reaction of phenylenediamines and 2-aminophenols (I) with nitroalkanes (II) in PPA leads to desired benzimidazoles and benzoxazoles (III) in high yields, whilst the reaction with 2-nitro-1-phenylethan-1-one (IV) affords unexpected 2-phenyl substituted products.

The title compounds are obtained by a novel acid-mediated cascade transformation via the ANRORC (addition of nucleophile, ring opening, and ring closure) mechanism.

A modular approach to 3-substituted 2-quinolones via a cascade annulation reaction between 4-nitroketones and hydrazines has been developed.

The data on transformations of dialkyl azodicarboxylates and their analogues involving various substrates are generalized. Nucleophilic addition and oxidation, pericyclic reactions and reactions occurring under the Mitsunobu reaction conditions are considered. Ample opportunities for application of these compounds in fine organic synthesis are shown. The bibliography includes 245 references.

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.

3-Substituted 2-quinolones are obtained via a novel, metal-free transannulation reaction of 2-substituted indoles with 2-nitroalkenes in polyphosphoric acid. The reaction can be used in conjunction with the Fisher indole synthesis offering a practical three-component heteroannulation methodology to produce 2-quinolones from arylhydrazines, 2-nitroalkenes and acetophenone.

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

Polynuclear aromatic and heteroaromatic compounds with peri-annelated fiveand six-membered rings include perimidine derivatives and show a range of useful properties. The development of novel, efficient methods for preparation of such compounds is a current challenge. Although methods for preparing perimidines containing a pyrrole ring are quite numerous [1-3], there are only very limited ways for synthesizing aceperimidines [3-5]. Such methods can be based on the dinitration of acenaphthene, reduction of the nitro derivative, and subsequent cyclization using various reagents. The drawback of such methods is the large number of stages. In our work, we propose a method of synthesizing aceperimidines from the available 4-acetyland 4-benzoylacenaphthenes 1a-e, using a system of reagents developed at our laboratories [6-8]. It was found that reaction of ketones 1a-e with a fourfold excess of sodium azide in polyphosphoric acid (PPA) for 1 h at 70-80°C, followed by 4 h at 100-110°C gave the aceperimidines 3a-e in 27-46% yields.

Previously unknown tetraazapyrene derivatives of type (III) are prepared in a one-pot procedure.

Three of the title compounds are synthesized in moderate yields by reaction of naphthotriazine (I) with β-nitrostyrenes.

Previously unknown title compounds are smoothly synthesized by treatment of perimidines (I) with β-nitrostyrene via in situ generated oximes and subsequent Beckmann rearrangement.

A new method for the relatively easy introduction of carbamoyl and carboxyl groups into activated aromatic compounds is presented.

The tandem transformation Schmidt-reaction—nitrosation—heterocyclization leads to previously unknown tetraazacyclopenta[c,d]phenalenes (II) together with N-oxides (III) as main products.

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

Possible reaction mechanisms leading to both peri-anellation products (III) and (IV) are proposed.

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

Using the reagent combination sodium azide/polyphosphoric acid, this one-pot, consecutive reaction of sodium azide and dicarbonyl compounds (II) with an aromatic compound (I) affords the quinolines (III) in low to moderate yields.

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.

The feasibility of the peri-annelation of the pyrrole ring to obtain perimidines by means of electrophilic amination using sodium azide in PPA is demonstrated.

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.

An effective synthesis has been developed for 2,3′-biquinolyls using nucleophilic addition of sodium hydride to quinoline and its alkyl derivatives.

It has been shown that the reaction of 2, 3′-biquinolyls with an excess of lithium in tetrahydrofuran leads to the formation of dianions, treatment of which with water or D2O gives 1′, 4′-dihydro-2, 3′-biquinolyls or their 4′-D derivatives in good yield. Oxidation of the latter leads to 4′-D-2,3′-biquinolyl. The reduction of 2, 3′-biquinolyl has been studied.

The synthesis of title compounds (III) from acetylperimidines (II) involves the formation of an amide intermediate which reacts with triazines or carboxylic acids.