Trifluoroacetylation of 9-methylcarbazole. 2. Peculiarities of the reaction due to the presence of trifluoroacetic acid

A satisfactory model of the intermediate in the formation of polyaryltrifluoromethylmethanes in the trifluoroacetylation of 9-methylcarbazole is 1,1,1-trifluoro-2,2-bis(9-methyl-3-carbazolyl)-2-hydroxyethane. The kinetic isotope effect of the reaction was evaluated. It is shown that the rate of the reaction is determined by the formation of a complex. The trifluoromethylation of 9-methyl-carbazole at 110C is accompanied by demethylation of the substrate under the influence of trifluoroacetic acid.See [1] for communication 1.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 329–336, March, 1987.     

9-alkenylcarbazoles. 13. Trifluoroacetylation of trans- and cis-9-alkenylcarbazoles

The trifluoroacetylation of 9-alkenylcarbazoles in pyridine takes place regio- and stereospecifically with the formation of the -trifluoroacetyl derivatives. The cis isomers are inert to trifluoroacetic anhydride.For Communication 12, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1066–1069, August, 1988.     

Trifluoroacetylation of 3-halo-9-methylcarbazoles

Trifluoroacetylation of 3-halo-9-methylcarbazoles at 110C proceeds at 6-position. In the case of 3-bromo- and 3-iodo-derivatives, the reaction is complicated by competing processes of dehalogenation, followed by the halogenation of the substrate, leading to 3,6-dihalo derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1492–1495, November, 1987.     

Synthesis of acetylene derivatives of 9-methylcarbazole

A number of mono- and diacetylene derivatives of 9-methylcarbazole were synthesized.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2634–2636, November, 1991.     

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.     

The Bargellini reaction in a series of heterocyclic thiols

The synthesis of sterically hindered carboxylic acids based on heterocyclic thiols has been performed via the Bargellini reaction. Structure of the obtained compounds has been confirmed by means of X-ray diffraction analysis.     

Studies in the heterocyclic series. XXI. A novel tetraaza-analog of phenothiazine

As a continuation of our search for new pharmaco-active phenothiazine compounds, the synthesis of 1,4,6,8-tetraazabenzo[b]phenothiazine ring system is described. Derivatives of this new heterocycle were prepared by converting 4,5-diamino-6-hydroxypyrimidine to 4,5-diaminopyrimidine-6-(1H)thione followed by the action of 2,3-dichloroquinoxaline in refluxing DMF or DMAC. The reaction of mixed nitric and sulfuric acids with 9-amino-12-chloro-1,4,6,8-tetraazabenzo[b]phenothiazine gave 9-amino-12-chloro-13-nitro-1,4,6,8-tetraazabenzo[b]phenothiazine 5-oxide in satisfactory yields. Diazotization of 9-amino-1,4,6,8-tetraazabenzo-[b]phenothiazine led to 1,4,6,8-tetraazatriazolo[4,5,1-kl]benzo[b]phenothiazine which is a new heterocyclic compound and the parent compound of this ring system. The mechanistic pathways to these compounds are also proposed.     

Nucleophilic photosubstitution of halogen in the heterocyclic series

A new method is described for the introduction of a cyano group into pyridine and pyrimidine rings and for the introduction of nitro and thiocyano groups into the pyridine ring by UV irradiation of halo-substituted pyridines and pyrimidines in the presence of the appropriate nucleophiles.     

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.     

Mannich reaction in a series of six-membered heterocyclic γ-ketones

It was established by PMR spectroscopy and mass spectrometry that the aminomethylation of 2,2-dimethyl-substituted oxygen-, sulfur-, and nitrogen-containing six-membered cyclic γ- ketones gives the corresponding 5-aminomethyl derivatives.     

Semicarbazones and thiosemicarbazones of the heterocyclic series

Isatin 2-thioxohydrazones formed in the reaction of isatin O-methyl ether with thioxohydrazines can be isolated in iminohydrazine and aminohydrazone tautomeric forms. The effect of the structure of the hydrazone fragment and the medium on the interconversions of the tautomers was investigated.See [1] for communication 42.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 355–359, March, 1979.     

Semicarbazones and thiosemicarbazones of the heterocyclic series

IsatinΒ-thiosemicarbazone and its alkyl derivatives containing a hydrogen atom attached to N_(2′) exist primarily in the form of the syn isomer stabilized by intramolecular hydrogen bonding in solutions and in the crystalline state. The strength of this hydrogen bond increases when both hydrogen atoms in the primary thioamide group are replaced by alkyl groups.     

Studies in the heterocyclic series XVII. A new type of triazaphenothiazine heterocycle

The synthesis of derivatives of 1,4,6-benzo[b]triazaphenothiazine, a novel aza-analog of phenothiazine, is described. The parent compound was obtained by base-catalysed condensation of 3-amino-2-mercaptopyridine with 2,3-dichloroquinoxaline in aqueous DMF. Several derivatives were also prepared by using the appropriately substituted aminomercaptopyridines and dichloro-quinoxalines. Nitration with mixed nitric and sulfuric acids gave the corresponding 13-nitro-1,4,6-benzo[b]triazaphenothiazine derivatives. The structures were elucidated by chemical evidence and by a study of their infrared, ultraviolet, pmr and mass spectra.     

Studies in heterocyclic polymers. Part VI. A weight-loss study of the formation of a polybenzoxazole

The cyclisation of an aromatic poly(o-hydroxyamide) to form polybenzoxazole has been studied by combining isothermal weight-loss and thermogravimetric analyses. The thermogravimetric data were analysed by the method of Gyulai and Greenhow [4] to derive values for the apparent activation energy of the cyclisation process which was found to double at about 50% conversion (74–155 kJ mole^?1. A similar result was observed when the process was studied in the presence of low concentrations of p-toluene sulphonic acid, which appears to have a moderate catalytic effect upon the cyclisation process. The apparent order of reaction of the process has been found to be close to 2, contrary to previous studies which have assumed it to be unimolecular.     

Synthesis of chloro aldehydes of the heterocyclic series

A method was developed for the preparation of 4-chloro-5-formylimidazolones, Δ⁴-thiazolinones, and 4-chloro-5-formyluracils by reaction of 4-azolidones or barbituric acids with dimethylformamide and phosphorus oxychloride.     

Chemistry of heterocyclic quinoneimines. 9. Reaction of benzo[a]phenoxazin-9-one with C-nucleophiles

Selective replacement of the hydrogen atom in the 5 position of the aromatic fragment of the substrate by the residue of a C-nucleophile, which is accompanied by rearrangement of the benzoquinoid structure to a naphthoquinoid structure, occurs in the reaction of benzo[a]phenoxazin-9-one with cyanoacetic acid derivatives under conditions of activation of the reagent.See [1] for Communication 8.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 538–541, April, 1988.     

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.     

Investigation of heterocyclic quinones XXV. Tautomeric and covalent hydration in the quinazolinequinone series

The tautomeric forms of 2-phenyl-4-hydroxy-8-piperidinoquinazoline-5,6-quinone were determined quantitatively by means of UV spectroscopy. It is shown that quinazolinequinones are not capable of covalent hydration.     

The Mitsunobu reaction in the chemistry of nitrogen-containing heterocyclic compounds. The formation of heterocyclic systems (review)

Methods for the design of nitrogen-containing heterocyclic systems involving the formation of C-N bonds under the conditions of the Mitsunobu reaction are discussed. Dedicated to Afanasi Andreevich Akhrem on his 95th birthday. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 347–385, March, 2008.