Researches on imidazoles

Reaction of 1,2-dialkylbenzimidazoles with -halogenoketones followed by cyclization of the 1,2-dialkyl-3-ß-ketoalkyl(aralkyl)-benzimidazolinium halides in aqueous solution, in the presence of bases, leads to the synthesis of a number of derivatives of a new aromatic tricyclic system, 4H-pyrrolo[1,2-a]benzimidazole.For Part XXXII see [8].     

Researches on imidazoles

A number of 1-alkyl (1, 2-dialkyl)-4-nitro-5-alkyl (aryl, dialkyl) aminoimidazoles are synthesized by reacting 1-alkyl (1, 2-dialkyl)-4-nitro-5-chloroimidazoles with aliphatic, aromatic, and heterocyclic amines. Hydrogenation of 1-ethyl-2-methyl-4-nitro-5-(N-morpholino) imidazole in acetic anhydride gives 1-ethyl-2-methyl -4-diacetylamino-5-(n-morpholino) imidazole, characterized as its picrate.Paper presented at the All-Union Conference on the Chemistry of Five-Membered Heterocyclic Rings, Rostovon-Don, 1962.     

Researches on imidazoles

A number of derivatives of imidazo [5, 1-b] thiazole, imidazo [5, 1-b] thiazoline, and imidazo [5, 1-b] thiazolid-3-one are synthesized by cyclizing 2-alkyl-4(5)-nitro-5(4)-formylmethyl (-ketoalkyl-,-hydroxyethyl-, and carboxymethyl) mercaptoimidazoles.For Part XXVI see [18].     

Researches on imidazoles

The 1-methyl-4, 5-dihalogeno-and 1-methyl-2, 4, 5-trihalogenoimidazoles resulting from reacting N, N-dimethyloxamide with phosphorus pentachloride or pentabromide, are formed by secondary reaction, halogenation of 1-methyl-5-halogenoimidazoles by the phosphorus pentahalides, which also halogenate other imidazoles derivatives, e. g., 1, 2-dialkyl-5-chloroimidazole and 2-alkylimidazoles at the free position in the nucleus.For Part XV see [1].     

Researches on imidazoles

The effective anti-Trichomonas preparation 1-(-hydroxyethyl)-2-methyl-5-nitroimidazole(metronidazole) is synthesized, as well as its 4-nitro derivative, and a number of other 2-methylimidazole derivatives: 1-(-hydroxyethyl)-2-methylimidazole, 1-(, -dihydroxypropyl)-2-methyl-4-nitroimidazole, and nitric acid esters of 1-(-hydroxyethyl)-2-methyl -4(& 5)-nitroimidazoles.     

Research on imidazoles

The reactivity of the methylene group of 5-phenyl and a, G-diphenylimidazo [2, 1-b]thiazolid-3-ones is investigated. The corresponding alkylidene, arylidene, and azomethine derivatives are prepared by reaction with, respectively, aldehydes, isatin, and nitro compounds. Diazonium salts give azo coupling products whose IR spectra show then to be 2-arylhydrazines of imidazo[2, 1-b]thiazolid-2, 3diones.For Part XXXIII see [18]     

Trifluoromethyl imidazoles

Some imidazole derivatives with trifluoromethyl substituents have been made, as part of a programme on the synthesis of fluorine-containing annyti-cancer agents. This work is a joint project between ourselves and Professor A.B. Foster's group at the Institute of Cancer Research, Royal Cancer Hospital, London. Imidazole carboxylic acids have been treated with sulphur tetrafluoride to give 2-trifluoromethyl-, 2,4-bis(trifluoromethyl)-, and 2,4,5-tris(trifluoromethyl)-imidazole. Some reactions of these trifluoromethyl derivatives have been studied. Ranges of N-substituted derivatives have been synthesised using the imidazole silver salts and the appropriate alkyl halide derivative. Hydrolytic stabilities of the CF₃ groups in the patent imidazoles have been studied.The 2-trifluoromethyl derivative is the least stable hydrolytically.     

Synthesis of imidazoles

Conclusions The synthesis of 4-alkylimidazoles was carried out by heating (2-oxoalkyl)triethylammonium bromides with formamide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No, 1, pp. 140–143, January, 1989.     

Synthesis of imidazoles

Silica gel was found to facilitate the conversion of 3-bromo-2-alkanones to imidazoles by the action of formamide. The selective 3-bromination of 2-alkanones was carried out in ethyl acetate.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 511–513, February, 1991.     

Syntheses of polyalkylated imidazoles

We have developed improved general simple methods for large-scale preparation of polyalkylated imidazoles by improved multicomponent synthesis from commercially available starting materials. A large range of NH- and N-alkyl-polyalkylimidazoles (40 in total, including novel compounds) has been synthesized.     

Direct hydroxylation of imidazoles

It is shown that the N-substituted derivatives of 4,5-diphenylimidazole, benzimidazole, naphth[1,2]imidazole, perimidine, and aceperimidine are hydroxylated by alkali metal hydroxides to give the corresponding 2-imidazolones and perimidones in high yields.The material in this paper regarding the synthesis of perimidones and aceperimidones should be considered as communication V of our series entitled Heterocyclic Analogs of Pleiadiene. See [16] for communication IV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 124–128, January, 1971.     

Synthesis on templates : Regiospecific synthesis of imidazoles

A new, biomimetic template operated strategy has been developed leading to regiospecific synthesis of imidazoles (CHARTS I & II).     

Microwave-assisted synthesis of sydnonyl-substituted imidazoles

3-Aryl-4-formylsydnones 1a-d react with symmetrical 1,2-dicarbonyl compounds, such as benzil (2a), 4,4′-dimethoxybenzil (2b), 4,4′-difluorobenzil (2c), and di-2-thienylethanedione (2d), in glacial acetic acid, using ammonium acetate as the ammonia source, to yield 4,5-diaryl-2-sydnonyl-substituted imidazoles 3a-6d under conventional heating. In a similar treatment, 4,5-diaryl-2-sydnonyl-1-substituted imidazoles 8a-10a can be prepared by the one-pot condensation of 3-(4-ethoxyphenyl)-4-formylsydnone (1d), benzil derivatives, ammonium acetate, and primary amines. However, such reactions, which take 1-3 days at high temperature under classical conditions, are completed successfully within a few minutes under microwave irradiation.     

Novel halogenated imidazoles. Chloroimidazoles

With one exception chloroimidazoles containing an unalkylated ring nitrogen have been ignored. Procedures are described using hypochlorite solution that permit the synthesis of 4,5-dichloroimidazole and 2,4,5-trichloroimidazole. Various bromoimidazoles are also converted to chloroimidazoles in refluxing hydrochloric acid.     

Organosodium compounds of N-substituted imidazoles

The corresponding 2-sodioimidazoles were obtained from N-substituted imidazoles and phenylsodium. If the 2 position of imidazole is occupied, the 5-sodio derivative is formed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1554–1555, November, 1970.     

A one step synthesis of 4-substituted imidazoles. An important observation when N-alkylating imidazoles

Imidazoles substituted in the 2-position with methyl, 1e , phenyl, 1a , 2-imidazole, 1b-d , or t-butyldiphenylsilyl, If, react with soft electrophiles 2 to give modest yields of 4(5)-C-alkylated-imidazoles 3 and N-alkylated products 5. These two products are readily separated by flash chromatography.     

Oxidative rearrangement of imidazoles with dimethyldioxirane

Tetrahydrobenzimidazoles, on treatment with dimethyldioxirane, rearrange to provide 5-imidazolones exclusively. These rearrangements proceed with a broad range of substrates and with good to excellent levels of diastereoselectivity. [reaction: see text]     

Mass spectra of some substituted imidazoles

Comparison of fragmentation pathways and high resolution measurements has revealed that the molecular ions of 1-(2-hydroxy-2-phenylethyl)imidazoles undergo elimination of benzaldehyde. The parent ions of trans-1-styrylimidazoles also cyclise in a manner similar to their photochemical reactivity. A rearrangement involving OH or OMe transfer between the trans-1-styryl and 5-acid or 5-methyl ester group of an imidazole is also described.