Synthesis and transformations of 2,3-dioxo-2,3-dihydroimidazo [1,2-a]-benzimidazole derivatives

9-(H)Alkyl-2,3-dioxo-2,3-dihydroimidazo[1,2-a]benzimidazoles were synthesized by the action of oxalyl chloride on 2-amino-1(H)alkylbenzimidazoles and subsequent cyclization of the resulting 2-amino-1-(H)alkyl-3-chlorooxalylbenzimidazolium chlorides in the presence of triethylamine. The behavior of the synthesized benzimidazoles with respect to the action of alkalis, lithium aluminum hydride, and ethylmagnesium bromide was studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1391–1395, October, 1976.     

Derivatives of phenyl-2,3-dihydroimidazo[1,2-a]pyridinone

The title compounds were prepared by the condensation of a series of β-keto esters with 2-benzylimidazoline. A mechanism is proposed wherein the dienamine 4 undergoes an intramolecular acylation with the elimination of ethoxide and subsequent hydride shift.     

Synthesis of 5-Phenyl-7-trifluoromethyl-2,3-dihydroimidazo[1,2-a]pyridines

Syntheses are reported for a series of 2-alkylamino-6-phenyl-4-trifluoromethylpyridines. The reaction of 3-cyano-2-(hydroxyalkylamino)-6-phenyl-4-trifluoromethylpyridines with thionyl chloride gave the corresponding 2-(chloroalkylamino)pyridines, 8-cyano-5-phenyl-7-trifluoromethyl-2,3-dihydro-imidazo[1,2-a]pyridines, and 9-cyano-6-phenyl-8-trifluoromethyl-2,3,4-trihydropyrido[1,2-a]-pyrimidines. X-ray diffraction structural analysis was used to study 8-cyano-5-phenyl-7-trifluoromethyl-2,3-dihydroimidazo[1,2-a]pyridine.     

Synthesis and insecticidal bioactivities of 2,3-dihydroimidazo[1,2-a]pyridin-5(1H)-one derivatives

A novel synthesis of 2,3-dihydroimidazo[1,2-a]pyridin-5(1H)-one, and insecticidal derivatives were described.     

Research on imidazo[1,2-a]benzimidazole derivatives. 22. Synthesis of 2,3-dihydroimidazo[1,2-a]benzimidazoles starting from 2-imino-3-(2-hydroxyethyl)benzimidazolines

A -elimination reaction with the formation of 2-imino-3-vinylbenzimidazolines occurs simultaneously with intramolecular alkylation and the formation of an imidazoline ring in the action of alcoholic alkali on 2-imino-3-(2-chloroethyl) benzimidazolines. The thermolysis of 3-chlorethyl-substituted imines without a solvent or in an inert solvent leads exclusively to 2,3-dihydroimidazo[1,2-a] benzimidazoles. An attempt to obtain the latter directly from 2-imino-3-(2-hydroxyethyl) benzimidazolines by the action of a mixture of thionyl chloride and acetic anhydride on them also leads to ambiguous results.See [1] for communication 21.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 918–925, July, 1986.     

A study of some 1-alkyl-2,3-dihydroimidazo[1,2-a]benzimidazoles

A series of 1-alkyl-7-nitro (and 7-amino)-2,3-dihydroimidazo[1,2-α]benzimidazoles has been prepared. Similarly, a series of 1-alkyl-2,3-dihydroimidazo[1,2-α]benzimidazoles has been prepared. The prototropic tautomerism of this system has been studied. The site of electrophilic attack (alkylation) has been examined. 1-Alkylation takes place under strongly basic conditions and 9-alkylation occurs under neutral conditions.     

Stepwise approach to the 2,3-dihydroimidazo[1,2-a]pyridine and 5-oxo-1,2,3,5-tetrahydroimidazo[1,2-a]pyridine ring systems

The syntheses of 2,3-dihydro-8-fluoro-6-trifluoromethylimidazo[1,2-a]pyridine-3-carbonitrile ( 2 ), 8-fluoro-6-trifluoromethylimidazo[1,2-a]pyridine-3-carbonitrile ( 9 ) and 5-oxo-8-trifluoromethyl-1,2,3,5-tetrahydroimidazo[1,2-a]pyridine-3-carbonitrile ( 3 ) are described. These compounds are constructed in a stepwise approach starting from the properly substituted 2-halopyridines.     

Nitration of 2,3-dihydroimidazo[1,2-a]benzimidazole and its N 9-substituted derivatives

7-Nitro-2,3-dihydroimidazo[1,2-a]benzimidazole and its N9-substituted derivatives can be conveniently synthesized by nitration of the corresponding tricyclic precursors with a nitrating mixture or with the HNO3 /CF3COOH system. This reaction occurs fairly smoothly and with good regioselectivity.     

Properties of 8-Cyano-5-phenyl-7-trifluoromethyl-2,3-dihydroimidazo[1,2-a]pyridines

The alkylation, acylation, halogenation, nitration, oxidation, and hydrolysis reactions of 8-cyano-5-phenyl-7-trifluoromethyl-2,3-dihydroimidazo[1,2-a]pyridine have been studied. It was found that the 6-halo derivatives add alcohol to give covalent solvates. X-ray analysis has been carried out on one of the solvates (6-chloro-8-cyano-7-ethoxy-5-phenyl-7-trifluoromethyl-1,2,3,7-tetrahydroimidazo[1,2-a]pyridine) as well as on 8-cyano-5-phenyl-7-trifluoromethyl-2,3-dihydroimidazo[1,2-a]pyridine trifluoroacetate.     

Synthesis and properties of pyrrolo[1,2-a]pyrazines (review)

The synthesis and properties of pyrrolo[1,2-a]pyrazines are reviewed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1299–1311, October, 1991.     

Properties of 2,3-dihydro-imidazolo[1,2-a]pyridines. (Review)

Published data on the physical and chemical characteristics of 2,3-dihydroimidazo[1,2-a]pyridines to 1998 are reviewed.Riga Technical University, Riga, Latvia; e-mail: mara@ktf.rtu.lv. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1011–1027, August, 2000.     

Influence of electronic and steric factors on 2,3-dihydroimidazo[1,2-a]pyridine-based enantioselective acylation catalysts

The catalytic activity and enantioselectivity of chiral 2,3-dihydroimidazo[1,2-a]pyridine (DHIP) derivatives was examined as a function of the steric environment of the nucleophilic nitrogen and the electronic properties of the pyridine ring. 2-Phenyl-6-trifluoromethyl-DHIP (CF₃-PIP) was confirmed to be the best catalyst in this series. In addition, three second-generation catalysts derived from the 1,2-dihydroimidazo[1,2-a]quinoline (DHIQ) core were tested and proved to be considerably more active than CF₃-PIP.     

2-Oxo-2,3-dihydroimidazo[2,1-a]isoquinoline and its transformations

2-Oxo-2,3-dihydroimidazo[2,1-a]isoquinoline (I) was synthesized by the action of -haloacetic acids on 1-aminoisoquinoline esters. The reactions of I with nitrous acid, acylating agents, aromatic aldehydes, p-nitrosodimethylaniline, and arenediazonium salts were studied. 3,3-Dihalo derivatives of this system with high reactivities of the halogen atoms were obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1666–1671, December, 1976.     

2,3-Diphenylthiazolo[3,2-a]pyrimidinium salts

The corresponding 2,3-diphenyl[3,2-a]pyrimidinium salts were obtained by the condensation of 4,5-diphenyl-2-aminothiazole perchlorate with -diketones, -chlorovinyl ketones, -chlorovinyl aldehydes, and 1,1,3,3-tetraethoxypropane. The PMR spectra were used to prove the structures of the compounds obtained, particularly to select the structures of the isomeric salts obtained in the condensation with unsymmetrical -diketones, -chlorovinyl ketones, and -chlorovinyl aldehydes. As a rule, the latter give one isomer — the -unsubstituted (relative to the bridge nitrogen atom) derivative.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 629–631, May, 1972.     

Synthesis of 2,3-Dihydroimidazo[1,2-a]pyridines from 1,3-Diketones

A series of 2-hydroxy-, 2-chloro-, and 2-(2-hydroxyethylamino)-6-aryl-4-polyfluoroalkyl-3-cyanopyridines has been synthesized. The latter react with phosphorus oxychloride to give fluorine containing 2,3-dihydroimidazo[1,2-a]pyridines.     

Synthesis of isoxazolo[2,3-a]quinoxalines and pyrrolo[1,2-a]quinoxalines by 1,3-dipolar cycloaddition reaction

The isoxazolo[2,3-a]quinoxalines 11a,b and pyrrolo[1,2-a]quinoxalines 12a,b were selectively synthesized from the 2-substituted 6-chloroquinoxaline 4-oxides 10a,b . The pyrrolo[1,2-a]quinoxalines 12a,b were clarified to be produced by the ring transformation of the isoxazolo[2,3-a]quinoxalines 11a,b . The pyrrolo[1,2-a]quinoxalines 14a,b were obtained from both 2,6-dichloroquinoxaline 4-oxide 9 and compounds 12a,b .