Research on imidazo[1,2-a]benzimidazole derivatives

The debenzylation of N-benzylimidazo[1,2-a]benzimidazoles with sodium in liquid ammonia was studied. The debenzylation of the 2-phenyl-substituted derivative is accompanied by hydrogenation of the outer imidazole ring to give 2-phenyl-2,3-dihydro-1H-imidazo[1,2-a]benzimidazole, the alkylation of which in alkaline media and neutral media, respectively, gives the 1-methyl derivative and the 9-methyl derivative. The 1-methyl derivative was subjected to quaternization and bromination; the latter proceeds in the condensed benzene ring. Debenzylation of the 2-methyl derivative of imidazo[1,2-a]benzimidazole is not accompanied by hydrogenation but gives 2-methyl-1(9)H-imidazo[1,2-a]benzimidazole.See [1] for communication VI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 791–796, June, 1973.     

Research on imidazo[1,2-a]benzimidazole derivatives

The action of excess nitrous acid on 9-methyl-2-phenylimidazo[1,2-a]benzimidazole results in opening of the outer imidazole ring and the formation of unstable 1-methyl-2-nitrosimino-3-oximinophenacylbenzimidazoline. The products of cleavage of this compound in alkali, acid, and alcohol solutions were studied.See [1] for Communication 18.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 68–70, January, 1980.     

Research on imidazo[1,2-a] benzimidazole derivatives

2-Acyl-substituted 3-methyl(phenyl)-9-methylimidazo[1,2-a]benzimidazoles were synthesized by three methods: by the reaction of -halo ketones with 3-benzoyl-2-imino-1-methylbenzimi-dazoline, by reaction of acetic anhydride or acetyl bromide with 1-methyl-2-phenacylaminobenzimidazole, and by acylation of 3-substituted imidazo[1,2-a]benzimidazoles. Some of the properties of the resulting 2-acyl-substituted compounds were studied.See [1] for communication XIV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 111–115, January, 1977.     

Research on imidazo[1,2-a]benzimidazole derivatives

Depending on the nature of the substituent in the 2 position of the heteroring, imidazo[1,2-a] benzimidazole derivatives undergo either mononitration in the 3 position or form dinitro derivatives. In the latter case, one nitro group enters the phenyl group in the 2 position, and the other enters the benzimidazole fragment of the molecule.     

Research on imidazo[1,2-a] benzimidazole derivatives

,-Unsaturated ketones of the imidazo[1,2-a]benztmidazole series were synthesized from 3-formyl- and 3-acetyl-substituted imidazo[1,2-a]benzimidazoles by crotonic condensation in the presence of alkaline catalysts. The ,-unsaturated ketones can also be obtained by direct acylation of 3-unsubstituted imidazo[1,2-a]benzimidazoles with the chlorides of unsaturated acids. The properties and pharmacological activity of the ketones obtained were studied.See [1] for communication XIII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1660–1665, December, 1976.     

Research on imidazo[1,2-a]benzimidazole derivatives XII. 3-Acyl-substituted imidazo[1,2-a]benzimidazoles

Stable 3-acetyl derivatives of imidazo[1,2-a]benzimidazole were synthesized by the action of acetic anhydride on 2,9-disubstituted imidazo[1,2-a]benzimidazole. The former were also obtained by cyclization of 1-alkyl (aralkyl) -3-acylmethyl-2-iminobenzimidazoline hydrobromides in acetic anhydride in the presence of anhydrous sodium acetate. 3-Benzoyl-substituted imidazo[1,2-a]benzimidazoles, which are unstable in acidic media, were synthesized by the action of benzoyl chloride in the presence of pyridine or excess starting imidazo [1,2-a] benzimidazole.See [1] for communication XI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 121– 125, January, 1976.     

Research on imidazo[1,2-a]benzimidazole derivatives XIII. Synthesis and properties of alcohols of the imidazo[1,2-a]benzimidazole series

Various hydroxy derivatives of imidazo[1,2-a]benzimidazole were synthesized from its 3-bromo, 3-formyl, and 3-acetyl derivatives. The properties and pharmacological activity of the products were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 126–134, January, 1976.     

Mass spectra of pyrrolo [1,2-a]benzimidazole and imidazo[1,2-a]benzimidazole derivatives

The closeness of the electronic structures of the ions formed in the first act of disintegration of the ions is responsible for the monotypic character of the subsequent fragmentation of pyrrolo[1,2-a]benzimidazole and imidazo[1,2-a]benzimidazole derivatives. The mass-spectrometric disintegration of the investigated systems has something in common with the fragmentation of thiazolo[3,2-a]benzimidazole derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, 1124–1127, August, 1975.     

Investigation of imidazo[1,2-a]benzimidazole derivatives

Esters of 1-alkyl- and 1-aralkyl-2-iminobenzimidazoline-3-acetic acids are converted to esters of 2,9-dimethylimidazo[1,2,-a]benzimidazole-3-carboxylic acid on heating with acetic anhydride. The brief action of acetic anhydride on the free iminobenzimidazolineacetic acids gives 2-oxo-2,3-dihydroimidazo[1,2-a]benzimidazoles, which are converted to 2,9-substituted 3-acetylimidazo[1,2-a]benzimidazoles on prolonged heating with acetic anhydride.See [1] for communication V.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 111–114, January, 1973.     

Research on imidazo[1,2-a]benzimidazole derivatives XI. Synthesis of 2-arylamino derivatives of 9-methylimidazo[1,2-a]benzimidazole

2-Arylamino derivatives of 9-methylimidazo[1,2-a]benzimidazole were obtained by cyclization of the products of the reaction of 2-amino-1-methylbenzimidazole with chloroacetic acid anilides. The former undergo diazo coupling and acetylation in the 3 position of the system, and the amino groups of secondary amines are also acetylated.See [1] for communication X.Translated from Khimiya Geterotsiklicheskikh, No. 10, pp. 1394–1398, October, 1975.     

Studies on derivatives of imidazo[1,2-a]benzimidazole

It has been found that 9-methyl-2-phenyl- and 2,9-dimethylimidazo[1,2-a]benzimidazoles undergo direct formylation at position 3. The formyl derivatives obtained take part in a series of condensations characteristic for aldehydes, but they do not undergo the Cannizzaro disproportionation.For Communication I, see [1].Translated from Geterotsiklicheskikh Soedinenii, Vol. 6, No. 6, pp. 838–841, June, 1970.     

Studies of imidazo[1,2-a]benzimidazole derivatives. 21. Synthesis of haloketones in the imidazo[1,2-a] benzimidazole series

Methods for the synthesis of imidazo[1,2-a]benzimidazole haloketone derivatives have been investigated. It has been found that -bromoketone derivatives of this heterocycle can be prepared either by bromination of 3-acylimidazo[1,2-a]benz-imidazoles with bromine in glacial acetic acid or by acylation of 3-unsubstituted imidazo[1,2-a]benzimidazoles with haloanhydride derivatives of -bromoalkanoic acids. Treatment of imidazo[1,2-a]benzimidazoles with 3-chloropropionyl chloride results in the formation of imidazo[1,2-a]benzimidazolyl-3-propionyl chloride and bis(imidazo[1,2-a]benzimidazolyl)propan-3-one derivatives as side products. Reaction of 2-phenylimidazo[1,2-a]benzimidazoles with 3-bromopropionic acid in polyphosphoric acid gives benzocyclohepten[5,6:4,5]imidazo[1,2-a]benzimidazole derivatives.For Communication 20, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 339–345, March, 1986.     

Research on imidazo[1,2-a]benzimidazole derivatives. 25. Reaction of 2,9-disubstituted imidazo[1,2-a]benzimidazoles with acrylic acids and their derivatives

The substitutive addition of acrylic acids and their esters, amides, and nitriles to 2,9-disubstituted imidazo[1,2-a]benzimidazoles, which leads to 3-(imidazo[1,2-a]benzimidazol-3-yl)propionic acids and their derivatives, was studied. The rate of addition depends on the structure of the unsaturated compound, the nature of the substituent in the 2 position, the magnitude of the charge on the carbon atom in the 3 position of the heteroring, and the reaction conditions. The addition proceeds most smoothly in polyphosphoric acid (PPA). In the case of acrylonitrile imidazo[1,2-a]benzimidazol-3-ylpropionic acid amides were isolated in PPA. In the reaction of - or -substituted acrylic acids with 2-phenylimidazo[1,2-a]benzimidazoles in PPA, in addition to the corresponding imidazo[1,2-a]benzimidazol-3-ylpropionic acids, products of their intramolecular cyclodehydration at the ortho position of the phenyl substituent are formed.See [1] for Communication 24.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1496–1502, November, 1987.     

One-pot synthesis of imidazo[1,2-b]pyrazole,imidazo[1,2-b]-1,2,4-triazole,imidazo[1,2-a]pyridine,imidazo[1,2-a]pyrimidine,imidazo[1,2-a]benzimidazole,and 1,2,4-triazolo[4,3-a]benzimidazole derivatives

Hydrazonoyl bromides 1a-c react with 5-amino-3-phenyl-1H-pyrazole, 5-amino-1H-1,2,4-triazole, 2-aminopyridine, and 2-aminobenzimidazole to afford the corresponding imidazol[1,2-b]pyrazoles 10, imidazo[1,2-b]-1,2,4-triazoles 11, imidazo[1,2-a]pyridines 16, imidazo[1,2-a]pyrimidines 17, and imidazo[1,2-a]benzimidazoles 20, respectively. Compounds 1a-c reacted also with 2-methylthiobenzimidazole to give 1,2,4-triazolo[4,3-a]benzimidazole derivatives 21. © 1997 John Wiley & Sons, Inc.     

Synthesis and reactions of imidazo[1,2-a]benzimidazole derivatives. I

Some reactions of imidazo[1, 2-a]benzimidazole derivatives have been studied: the cleavage of their quaternization products, bromination, and the replacement of the bromine in position 3.     

Imidazo[1,2-a]benzimidazole derivatives

3-Amino derivatives of 9-alkyl(benzyl)-2-arylimidazo[1,2-a]benzimidazoles, obtained by the reduction of the appropriate 3-nitro(nitroso) derivatives, are extremely unstable, and the imidazole ring opens readily resulting in conversion to 2-(-carboxybenzylamino)benzimidazoles. The reaction apparently proceeds through the intermediate formation of 2-(-cyanobenzylamino)benzimidazole, which is a tautomeric form of the 3-amino compound and can react as such to form 3-acylamino derivatives and anils. If there is a methyl group in the 3-position of the ring, the amine is quite stable and can be isolated in free form.See [1] for communication IV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 673–677, May, 1971.     

New pyrazino[1,2-a]benzimidazole derivatives

1-Ethoxycarbonyl-3-phenyl- and 3-phenylpyrazino[1,2-a]benzimidazoles were synthesized by reaction of 2-ethoxalyl- and 2-diethoxymethyl-N-phenacylbenzimidazoles, obtained from the corresponding sodium derivatives of benzimidazole and phenacyl bromide, with ammonium acetate.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1266–1267, September, 1976.     

Investigations in the field of imidazo[1,2-a]benzimidazole

The nitrosation and azo coupling reactions in the imidazo[1,2-a]benzimidazole series have been studied. Position 3 of the system undergoes attack. The nitroso compounds readily undergo hydrolysis in acid and alkaline media at the 1–2 bond with the formation of derivatives of benzimidazolone or 2-iminobenzimidazoline.For Communication II, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii.Vol. 6, No. 7, pp. 977–980, July, 1970.