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

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.

The literature concerning peri-annulation is reviewed. For the first time, peri-annulation methods are considered from the standpoint of the participation of functional groups in the formation of a new cycle. Special attention is focused on methods of peri-annulation that do not involve functional groups in peri-positions. The review is limited to the methods of producing five- and six-membered carbocyclic and nitrogen-containing heterocyclic rings.

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.

This review covers literature data on the amination of arenes and considers both multistep methods for the introduction of an amino group in the aromatic ring and the direct amination (amidation) of aromatic hydrocarbons. The main attention is drawn to the electrophilic amination (amidation) of aromatic hydrocarbons because of the lack of comprehensive reviews on recent advances in this area.

We describe an analog of the Cauchy-Kovalevskaya sufficient conditions for the analytic solvability of the Cauchy problem for systems of operator-differential equations of arbitrary order in locally convex spaces; this analog is stated in terms of the order and type of the linear operator.

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.

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.

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.

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.

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.

Nitration of acylperimidines (I) using NaNO2 in formic acid gives predominantly the 6(7)-nitro-derivatives (II), which can be smoothly transformed into tetraazapyrenes (IV) via a Schmidt Reaction, or triazacyclopentaphenalenes (V) via simple Zn-reduction.

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.

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.

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.

1,3-Diazapyrenes (IV) and (VI), tetrahydro-1,3-diazapyrenes (VIII) and 1,3,7-triazapyrenes (IX) are synthesized by three-component reactions of perimidines (I).

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

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

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.

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.

Development of new efficient synthetic methods for poorly available compounds possessing useful properties is an actual problem. Polynuclear aromatic and hetero aromatic compounds with peri annulated five membered rings belong to such compounds. If there are known plenty of methods for the peri annulation of pyrrole1—4 and furan4 ring to naphthalene derivatives, only several examples are described for the peri annulation of pyrazole ring.4—6 In the present work, we suggest a method for the syn thesis of compounds containing such a fragment, which is based on the reaction of electrophilic acetamidation of arenes with nitroethane in PPA recently discovered in our laboratory.7—9 We showed that the reaction of perimidines 1a—c and nitroethane in the molar ratio of 1 : 2 (Scheme 1) in the presence of catalytic amounts of DABCO in polyphos phoric acid (PPA) at 100—105 C for 3 h with subsequent addition of NaNO2 in the amount equimolar to that of nitroethane and heating for another 6 h at this tempera ture leads to 1,2,5,7 tetraazacyclopenta[c,d]phenalenes 5a—c in 26—33% yields. Earlier, such compounds were obtained in close yields using the following synthetic se quence: the Schmidt reaction—nitrosation5 (starting from 6(7) acetylperimidines) and amination of perimidines 1a—c with sodium azide in PPA with subsequent nitrosation.6 The method suggested in this work has the following ad vantages as compared to those developed earlier. First, it does not require preliminary functionalization of perim idines 1a—c; second, no use of sodium azide in acidic medium is needed and, therefore, no highly toxic and ex plosive HN3 is liberated. Probably, N oxides 4a—c were another reaction products, which were not isolated be cause of their good solubility in water. A suggestion on their formation made based on the Scheme shown below was confirmed by the fact that they were converted to 1,3,6,8 tetraazapyrenes 6a—c by the reduction with zinc dust. The yields of compounds 6a—c starting from perim idines 1a—c were 40—44%. It is probable that the reaction follows the following course. The acetamidation of perimidines 1a—c leads to acetamidamides 2a—c, whose nitrosation8 gives the inter Scheme 1