Diazo compounds of the heterocyclic series

Stable primary N-nitrosamines of the benzimidazole series were obtained by the action of sodium amide and isoamyl nitrite on 1-substituted 2-aminobenzimidazoles and subsequent acidification of the resulting benzimidazole-2-diazotates. The effect of the acidity of the solution on the activity of the benzimidazole-2-diazonium salts formed from the nitrosamines was traced.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 689–692, May. 1974.     

Diazo compounds of the heterocyclic series

2-(N-Nitrosamino)benzimidazoles in aqueous solutions or in organic solvents are spontaneously converted to 1,3-di(2-benzimidazolyl)triazenes. Other methods for the synthesis of triazenes of the benzimidazole series and their properties are examined.     

Amination of heterocyclic compounds with o-benzoylhydroxylamine derivatives

The N-amination of heterocyclic compounds 1a-k with O-benzoylhydroxylamine derivatives 5 was developed and demonstrated to be a superior alternative to existing N-amination methods. A structure-reactivity relationship study was performed on variously substituted O-benzoylhydroxylamine derivatives, leading to the discovery of the novel and more efficient aminating reagents 5h and 5i.     

Diazo compounds of the heterocyclic series. 4. Some peculiarities of the diazo coupling of benzimidazole-2-diazonium salts with phenols and their ethers

The corresponding hydroxy (methoxy)-substituted azobenzimidazoles were obtained by diazo coupling of benzimidazole-2-diazonium salts with phenols and their complete and incomplete ethers in strongly acidic media; in the case of phenol ethers the process is complicated by dealkylation of the methoxy group in the ortho position relative to the azo bridge.See [1] for Communication 3.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 637–642, May, 1990.     

Studies in the heterocyclic series. XX. 1,4-Diazaphenoxazine and related compounds

As part of our program on the synthesis of new psychotropic agents, the parent rings of two diazaphenox-azines are described. The reaction of 2-aminophenol and 2,3-dichloropyrazine in alkaline media gave good yields of 1,4-diazaphenoxazine. Replacement of 2,3-dichloropyrazine with 2,3-dichloroquinoxaline gave on the other hand the heterocycle, 1,4-diazabenzo[b]phenoxazine. Nitration and S-oxide formation were achieved by reaction with mixed nitric and sulfuric acids. Mechanistic pathways to these compounds were also discussed.     

Structure-mesomorphic activity relationship in the series of nitrogen-containing heterocyclic compounds

The structure-mesomorphic activity relationship was studied using the SARD (Structure Activity Relationship and Design) system for 300 nitrogen-containing heterocyclic compounds of which 178 compounds form a liquid crystal mesophase. Structural fragments exerting positive and negative effects on the manifestation of mesomorphic properties were revealed.     

Fluorinated heterocyclic compounds. 4-fluoro-2-pyridone

The uracil analog, 4-fluoro-2-pyridone was synthesized by ether cleavage of 4-fluoro-2-methoxypyridine with trimethylsilyl iodide. Improved procedures for the preparations of 2-methoxypyridine N-oxide hydrochloride and 2-methoxy-4-nitropyridine N-oxide are described.     

Introduction of the pyrylium ring into compounds of the aromatic and heterocyclic series

Halogen-substituted pyrylium cations react with organic nucleophilic compounds via an electrophilic mechanism to form new pyrylium salts. The reaction is extended to aromatic, heterocyclic, andnonbenzoid aromatic systems. Pyrylium salts that contain other functional groups do not enter into this reaction. The IR spectra of the compounds obtained are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1320–1323, October, 1971.     

Regioselective photoalkylation of 2-cyano-6-methoxynaphthalene by methoxy-substituted 1,2-diarylcyclopropanes

Photoreactions of 2-cyano-6-methoxynaphthalene with methoxy-substituted 1,2-diarylcyclopropanes in benzene give 2-cyano-1-(1,3-diarylpropyl)-6-methoxynaphthalenes. The excellent regioselectivity seen in these processes can be explained by initial formation of singlet exciplexes, in which the dipoles of each component are oriented in opposite directions.     

Studies on the synthesis of heterocyclic compounds. Part I. The pschorr reaction in the pyrazole series

Preparation and structural evidence of N-methyl-(1,3-R,R'-pyrazol-5-yl)-o-nitrobenzamides (VIIIa, b) are discussed. Diazotisation of related o-aminobenzamides XIa,b followed by the Pschorr reaction afforded a very complex mixture from which pyrazolo[3,4-c]isoquinolin-5-ones XIIa.b in 7–10% yields together with N-methyl-(1,3-R,R'-pyrazol-5-yl)-o-hydroxybenzamides (XIIIa) in 15–20% yields were isolated.     

Flash vacuum pyrolysis of methoxy-substituted lignin model compounds

The flash vacuum pyrolysis (FVP) of methoxy-substituted beta-O-4 lignin model compounds has been studied at 500 degrees C to provide mechanistic insight into the primary reaction pathways that occur under conditions of fast pyrolysis. FVP of PhCH(2)CH(2)OPh (PPE), a model of the dominant beta-O-4 linkage in lignin, proceeds by C-O and C-C cleavage, in a 37:1 ratio, to produce styrene plus phenol as the dominant products and minor amounts of toluene, bibenzyl, and benzaldehyde. From the deuterium isotope effect in the FVP of PhCD(2)CH(2)OPh, it was shown that C-O cleavage occurs by homolysis and by 1,2-elimination in a ratio of 1.4:1, respectively. Methoxy substituents enhance the homolysis of the beta-O-4 linkage, relative to PPE, in o-CH(3)O-C(6)H(4)OCH(2)CH(2)Ph (o-CH(3)O-PPE) and (o-CH(3)O)(2)-C(6)H(3)OCH(2)CH(2)Ph ((o-CH(3)O)(2)-PPE) by a factor of 7.4 and 21, respectively. The methoxy-substituted phenoxy radicals undergo a complex series of reactions, which are dominated by 1,5-, 1,6-, and 1,4-intramolecular hydrogen abstraction, rearrangement, and beta-scission reactions. In the FVP of o-CH(3)O-PPE, the dominant product, salicylaldehyde, forms from the methoxyphenoxy radical by a 1,5-hydrogen shift to form 2-hydroxyphenoxymethyl radical, 1,2-phenyl shift, and beta-scission of a hydrogen atom. The 2-hydroxyphenoxymethyl radical can also cleave to form formaldehyde and phenol in which the ratio of 1, 2-phenyl shift to beta-scission is ca. 4:1. In the FVP of o-CH(3)O-PPE and (o-CH(3)O)(2)-PPE, products (ca. 20 mol %) are also formed by C-O homolysis of the methoxy group. The resulting phenoxy radicals undergo 1,5- and 1,6-hydrogen shifts in a ratio of ca. 2:1 to the aliphatic or benzylic carbon, respectively, of the phenethyl chain. In the FVP of (o-CH(3)O)(2)-PPE, o-cresol was the dominant product. It was formed by decomposition of 2-hydroxy-3-hydroxymethylbenzaldehyde and 2-hydroxybenzyl alcohol, which are formed from a complex series of reactions from the 2, 6-dimethoxyphenoxy radical. The key step in this reaction sequence was the rapid 1,5-hydrogen shift from 2-hydroxy-3-methoxybenzyloxy radical to 2-hydroxymethyl-6-methoxyphenoxy radical before beta-scission of a hydrogen atom to give the substituted benzaldehyde. The 2-hydroxybenzyl alcohols rapidly decompose under the reaction conditions to o-benzoquinone methide and pick up hydrogen from the reactor walls to form o-cresol.     

Sigma complexes in the pyrimidine series. 2. σ Complexes of 5-nitropyrimidine and methoxy-substituted 5-nitropyrimidines with the acetone anion

The corresponding σ complexes of the Meisenheimer type, viz., anions of the potassium salts of 6H-5-nitro-6-acetonylpyrimidines, were obtained and isolated in the reaction of 5-nitro-, 5-nitro-4-methoxy-, 5-nitro-2-methoxy-, and 5-nitro-2,4-dimethoxypyrimidines with acetone in the presence of potassium hydroxide. The structures of the complexes were proved by means of the PMR, IR, and UV spectra. It is shown that the acetone anion in all cases adds to the methoxy-unsubstituted position of the pyrimidine ring, whereas nucleophilic attack takes place at the C₄ atom when the 2 and 4 positions are free. See [1] for communication 1. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 239–242, February, 1980.     

X-ray emission spectroscopy and electronic. Structure of heterocyclic compounds 2. Thiophene

The electronic structure of has been studied by X-ray spectroscopy. SK , SL _2,3- and CK _±-spectra were obtained. Theoretical spectra were constructed on the basis of ab initio and MNDO calculations and the experimental results were interpreted. The HOMO is an orbital in which the electron density is localized on the carbon atoms. Conclusions about the occupancy of the lowest 3d orbital were reached from the experimental results.For Communcation 1, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1188–1193, September, 1993.     

Synthesis of heterocyclic compounds. XIII. 2-amino-3-benzyl-3,5-dieyano-6-methoxy-4-phenyl-3,4-dihydropyridines

A synthesis of 2-amino-3-benzyl-3,5-dicyano-6-methoxy-4-phenyl-3,4-dihydropyridines from benzylmalononitriles and benzylidenemalononitrile is described. The structures of the new compounds have been elucidated on the basis of spectral data (ir, nmr, ms), and in two cases (Vb and Ve) by chemical degradation.