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A method has been developed for the nitration of 6(7)-acylperimidines using sodium nitrite in formic acid. The reaction gives a mixture of 4(9)-, 9(4)-, and 7(6)-nitro-6(7)-acylperimidines from which the latter can be separated by extraction with chloroform. Reduction of the 6(7)-acyl-7(6)-nitro- perimidines yields 1H-1,5,7-triazacyclopenta[cd]phenalenes. Subsequent Schmidt reaction and reduction give 1,3,6,8-tetraazapyrenes.

Plants of the Amaryllidaceae family produce a large variety of alkaloids and non-basic secondary metabolites, many of which are investigated for their promising anticancer activities. Of these, crinine-type alkaloids based on the 5,10b-ethanophenanthridine ring system were recently shown to be effective at inhibiting proliferation of cancer cells resistant to various pro-apoptotic stimuli and representing tumors with dismal prognoses refractory to current chemotherapy, such as glioma, melanoma, non-small-cell lung, esophageal, head and neck cancers, among others. Using this discovery as a starting point and taking advantage of a concise biomimetic route to the crinine skeleton, a collection of crinine analogues were synthetically prepared and evaluated against cancer cells. The compounds exhibited single-digit micromolar activities and retained this activity in a variety of drug-resistant cancer cell cultures. This investigation resulted in the discovery of new bicyclic ring systems with significant potential in the development of effective clinical cancer drugs capable of overcoming cancer chemotherapy resistance., SCOPUS: ar.j, info:eu-repo/semantics/published

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.

Methods have been developed for the synthesis of 1,3-diazapyrenes, 8(6)-aryl-6(8)-oxo-1,6,7,8-tetra-hydro-1,3-diazapyrenes, and 1,3,7-triazapyrenes based on a three-component reaction of perimidines with 1,3,5-triazines and carbonyl compounds, benzonitrile, or vinyl butyl ether in polyphosphoric acid.

A new method of carboxyamidation of aromatic compounds based on their reaction with nitromethane in polyphosphoric acid has been developed. Upon the hydrolysis of benzamides during the reaction mixture workup, the corresponding benzoic acids can be obtained.

A method has been developed for the synthesis of aromatic amines by the amination of the corresponding aromatic compounds using sodium azide in PPA. A method for the synthesis of quinazolines and benzo[h]quinazolines using this reaction and the subsequent reaction of the intermediates with 1,3,5-triazines has been developed.

A method was developed for the synthesis of 1H-1,5,7-triazacyclopenta[c,d]phenalenes by the electrophilic amination of perimidines using the new sodium azide/PPA reagent system and a subsequent one-pot reaction with 1,3,5-triazines. A multicomponent variant of this reaction is possible in the case of 2,4,6-trimethyl- and 2,4,6-triphenyl-1,3,5-triazines.

The ability of elemental sulfur to interact with organic compounds to give practically useful products has been known for a long time [1, 2]. Undoubtedly, thiophene is the most important of sulfur-containing heterocycles. The value of thiophene and its derivatives is due not only to the multitude of their reactions but also to high biological activity and useful associated properties, e.g. anticancer [3-5], analgesic [6], and antiinflammatory [7]. Certain thiophene derivatives are used as technical dyes or polymer coatings [8, 9]. We have recently developed a method for the peri annelation of a thiophene ring to 1H-perimidine derivatives based on a benzoylation reaction of 6(7)-mercaptoperimidines by benzoic acid in polyphosphoric acid [10]. A marked drawback of this method is the poor availability of the starting compounds. In this work we now propose a novel method for peri annelation of a thiophene ring based on the use of very readily available carbonyl compounds of 1H-perimidine and 1,2,3-triazaphenalene. In our laboratory, a method had been devised for the thiolation of 2,3'-biquinolyl derivatives by the action of elemental sulfur with or without the presence of KOH [11, 12]. In these processes polysulfides acted as the thiolating agents and the reaction occurred as free radical process. We proposed that this scheme would also be effective for the thiolation of carbonyl compounds.

A method of synthesizing 6(7)-aminoperimidines has been developed based on the electrophilic amination of perimidines with sodium azide in PPA. The corresponding amides were synthesized by acylation and were also obtained by the Schmidt reaction from 6(7)-acetyl(or benzoyl)perimidines. A special feature of the structure of the 2-substituted amines and amides is the presence of annular tautomerism slow in NMR time.

A new method for the synthesis of 4H-benzo[de]isoquinolin-4-ones has been developed, based on the reaction of 2-naphthyl ethers with an equimolar quantity of 1,3,5-triazines in polyphosphoric acid. With a 2.5 molar excess of 1,3,5-triazines in polyphosphoric acid, the products of 1,6-diacylation (diformylation) are formed. Isoquino[6',5',4':10,5,6]anthra[2,1,9-def]isoquinoline is formed upon reaction of a 1.5 molar excess of 1,3,5-triazine with naphthalene in polyphosphoric acid at 130-140 °C.

The regioselectivity of quaternization of 1,3,5-triazapyrenes by alkyl halides has been studied. Oxidative hydroxylation of 1-alkyl- and 7-alkyl-1,3,7-triazapyrenium salts gives 1-alkyl-1,2-dihydro-1,3,7-triazapyren-2-ones or 7-alkyl-6,7-dihydro-1,3,7-triazapyren-6-ones respectively. In the absence of an oxidant the hydroxylation of the 1-alkyl-1,3,7-triazapyrenium salts leads to a hydrolytic cleavage of the heterocycle.

The nitration of 1'-alkyl-1',4'-dihydro-2,3'-biquinolin-4'-ones and 1'-alkyl-1',2'-dihydro-2,3'-biquinolin-2'-ones has been investigated. It was shown that the regioselectivity of nitration of the first depends on the acidity of the medium and the order of adding reactants. In strongly acidic medium 1'-alkyl-5,6'-dinitro-1',4'-dihydro-2,3'-biquinolin-4'-ones or mixtures of them with 1'-alkyl-5-nitro-1',4'-dihydro-2,3'-biquinolin-4'-ones are formed. In less acidic media 1'-alkyl-6'-nitro-1',4'-dihydro-2,3'-biquinolin-4'-ones and then 1'-alkyl-6,6'-dinitro-1',4'-dihydro-2,3'-biquinolin-4'-ones are formed. Nitration of 1'-alkyl-1',2'-dihydro-2,3'-biquinolin-2'-ones leads to 1'-alkyl-6'-nitro-1',2'-dihydro-2,3'-biquinolin-2'-one and then 1'-alkyl-6,6',8'-trinitro-1',2'-dihydro-2,3'-biquinolin-2'-one.

A method has been developed for the synthesis of 4-(2-quinolinyl)-1,2,3,3a - tetrahydropyrrolo-[1,2-a]quinolines based on the 1,3-dipolar cycloaddition reaction of α,β-unsaturated carbonyl compounds to 2,3'-biquinolinium salts. Oxidation in benzene using Mn0 2 gave 4-(2-quinolinyl)-pyrrolo[1,2-a]quinolines. It was found that a side product of the 1,3-dipolar cycloaddition is 7,14-dibenzoyl-6,13-di(2-quinolyl)-6a,7,13a,14-tetrahydro-7a,14a-diazadibenzo[a,h]anthracene.Reaction of 1'-phenacyl-2,3'-biquinolinium salts with hydroxylamine in acetic acid gave 4-(2-quinolyl)imidazo-[1,2-a]quinolines.

Published data on the recyclization reactions of 1,3,5-triazines are reviewed. The classification is based on the fragments of the 1,3,5-triazine molecules used in the construction of new heterocycles.

Methods have been developed for the synthesis of 1,3-diazapyrenes based on the reactions of perimidines with ethoxymethylene-1,3-dicarbonyl compounds and also 6(7)-benzoyl(acetyl, formyl)perimidines with carbonyl compounds in PPA.

A novel three-component synthesis has been developed for 1,3-diazapyrenes based on the reaction of 1,8-naphthalenediamine with triazine and carbonyl compounds in polyphosphoric acid (PPA). The use of benzonitrile in place of the carbonyl compounds in this reaction gives 6-phenyl-1,3,7-triazapyrenes.

Methods have been developed for the synthesis of 2,3′-biquinolines, their 1′,4′-dihydro derivatives, 3-pyrid-2-ylquinolines, and 3-pyrazin-2-ylquinoline based on the interaction of hetarylethylenes and vinyl butyl ether with imidoyl chlorides and Vilsmeier complexes. Using the example of the synthesis of 3-hetarylquinolines and their dihydro derivatives the synthetic possibilities of the Vilsmeier method were shown for creating various bonds in different quinoline nuclei of the bisheterocyclic system.

A method has been developed for the synthesis of 1,3,7-triazapyrenes using the reaction of 6(7)-formyl-and 6(7)-benzoylperimidines with 1,3,5-triazines in PPA. Under these conditions, 6(7)-formylperimidine reacts with 2,4,6-trimethyl-1,3,5-triazine to give 6-hydroxy-1,3-diazapyrene.

A new effective synthetic method for 1,3-diazapyrenes and 1,3,7-triazapyrenes is developed based on the three-component reaction of perimidines or 1,8-diaminonaphthalene with 1,3,5-triazines and carbonyl compounds or benzonitrile in polyphosphoric acid (PPA).

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.

PPA-induced umpolung triggers efficient nucleophilic addition of unactivated anilines to nitroalkanes to produce N-hydroxyimidamides. The latter undergo sequential acid-promoted cyclocondensation with ortho-OH or ortho-NHR moieties to afford benzoxazoles and benzimidazoles, respectively.

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.

Methyl and ethyl 2-(2-oxo-2,3-dihydro-3H-indol-3-ylidene)acetates react with aromatic amines to give products of regioselective addition at the α-position of the activated exocyclic C=C bond, methyl and ethyl 2-arylamino-2-(2-oxo-2,3-dihydro-1H-indol-3-yl)acetates.

A method has been developed for the synthesis of bromo and chloro derivatives of 2,3′-biquinoline and 2,3′-biquinolones based on the bromination and chlorination in various media. It was found that the bromination of 2,3′-biquinoline in strongly acidic medium occurred on the 2-quinoline fragment and in weak acid on the 3-quinoline and that it takes place via a stage of formation of a dihydro derivative. 1′-Alkyl-1′, 4′-dihydro-2,3′-biquinolin-4′-ones and 1′-alkyl-1′,2′-dihydro-2,3′-biquinolin-2′-ones are halogenated at position 6′.

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.

Reactions of perimidines and perimidin-2-ones with α,β-unsaturated carbonyl compounds gave various 1,3-diazapyrene derivatives. Acylation of 1-methylperimidine, perimidin-2-one, and 1-methylperi-midin-2-one with cinnamoyl chloride in the presence of AlBr3 is accompanied by peri-fusion at the 6,7-position and dearylation of the intermediate product. Under analogous conditions, 1,3-dimethyl-2,3-dihydroperimidine gave rise to 6-cinnamoyl-1,3-dimethyl-2,3-dihydroperimidine. Reactions of perimidin-2-ones with 1,3-di-phenyl-2-propenone in polyphosphoric acid resulted in peri-fusion at the 6,7-position, and with acetylacetone, at the 1,9-position.

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.

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

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

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.

A new method of acetamidation of aromatic compounds based on their reaction with nitroethane in polyphosphoric acid has been developed. Upon the hydrolysis of acetamides during the reaction mixture workup, the corresponding amines can be obtained.