A. S. Morkovnik

Synthesis and some conversions of N-substituted benzimidazole-2-sulfonic acids

A series of N-substituted benzimidazole-2-sulfonic acids was synthesized in good yield by the N-alkylation of benzimidazole-2-sulfonic acids by alkylation with simple and functionalized alkylating agents under mild conditions. The corresponding N-substituted benzimidazolones and also primary, secondary, and tertiary amines were obtained by the action on the obtained compounds of alkali, ammonia, ammonium acetate, and amines.

Reactions of N-substituted diazoles and their halo derivatives with naphthyllithium and naphthylsodium

Abstract1-Methylimidazole and halo derivatives of some 1-substituted imidazoles and pyrazoles react with naphthyllithium(sodium) to give organolithium(sodium) compounds. 1-Benzyl-3, 5-dimethylpyrazole undergoes debenzylation on reaction with naphthyllithium.

Prototropic equilibrium in 1(11)H-2, 3, 4, 5-tetrahydro[1, 3]diazepino[1, 2-a]benzimidazole, synthesis and pharmacological properties of its N-substituted derivatives

Based on the X-ray crystallography and 1H NMR spectroscopy data and quantum chemical studies, it was found that 1(11)H-2, 3, 4, 5-tetrahydro[1, 3]diazepino[1, 2-a]benzimidazole (1) exists almost exclusively in the 1H-prototropic form. To prepare the fixed 11H-diazepinobenzimidazole forms of 1, 1-R-2-(4-chlorobutylamino)benzimidazoles (R = Me, N=CHAr) were synthesized, which underwent thermal cyclization with the formation of a mixture of 11-Rsubstituted diazepine 1 and 1-R-2-(pyrrolidin-1-yl)benzimidazole. Alkylation of diazepine 1 in a neutral medium regioselectively gave 11-R-diazepinobenzimidazoles in high yield. Their 1-substituted isomers were obtained by carrying out this reaction in the system NaH—THF. The N(11)-derivatives of diazepinobenzimidazole 1 were found to inhibit dipeptidyl peptidase 4 (DPP-4), but less actively than a comparator drug sitagliptin. The compounds under study did not exhibit antiglycation action in vitro and virtually did not affect activity of α-glucosidase and glycogen phosphorylase. However, they are characterized by a strong antiaggregant effect, making these derivatives promising for further studies.

Synthesis of 1(11)H-2,3,4,5-tetrahydro[1,3]diazepino[1,2-a]benzimidazole starting from benzimidazole-2-sulfonic acid. Intramolecular cyclization of 2-(δ-chlorobutylamino)benzimidazole

The intramolecular cyclization of 2-(δ-chlorobutylamino)benzimidazole (3c) follows the unusual pathway involving the predominant attack on the exocyclic amino group rather than on the much more nucleophilic endocyclic nitrogen atom. This reaction affords 2-pyrrolidinobenzimidazole and 1(11)H-2,3,4,5-tetrahydro[1,3]diazepino[1,2-a]benzimidazole as the major product and the by-product, respectively. The cyclization can be directed exclusively toward the annulation of the diazepine ring only after the acetylation of the amino group of compound 3c. According to the quantum chemical calculations, the unusual regioselectivity of the cyclization of chloramine 3c is associated primarily with a substantially less steric strain and the higher entropy of pyrrolidine transition states compared to diazepine transition states.

Synthesis of 9-bromocotarnine and its recyclization into 4-acyl-9-bromo-7,8-methylenedioxy-1,2-dihydro-3-benzazepines with anti-infective activity

Abstract9-Bromocotarnine in the stable perchlorate form has been obtained by the interaction of cotarnine with bromine. The reaction of 9-bromocotarnine with α-haloketones is accompanied by the extension of the six-membered hetero-ring to seven-membered ring and led to previously unknown 4-acyl-9-bromo-3-methyl-6-methoxy-7,8-methylendioxy-1,2-dihydro-3-benzazepines. Some of these compounds have been shown to have only moderate antibacterial (against Staphylococcus aureus, Escherichia coli) and fungistatic (Penicillium italicum) activities, but none of them has been shown to have a pronounced protistocidal activity against Colpoda steinii.

1-Amino-2-hydrazinobenzimidazole and its reactions with some carbonyl compounds

Abstract1-Amino-2-hydrazinobenzimidazole was obtained for the first time by treating 1-aminobenzimidazole-2-sulfonic acid with hydrazine hydrate. This compound readily condensed with aromatic aldehydes involving both amino groups. The condensation with 2,4-pentanedione affords 1-amino-2-(3,5-dimethylpyrazol-1-yl)benzimidazole, and with α-ketoacids in glacial acetic acid yields mixtures of 10-acetylamino-3-R-1,2,4-triazino[4,3-a]benzimidazol-4(10H)-ones and 4-amino-2-R-1,2,4-triazino[2,3-a]benzimidazol-3(4H)-ones.

Regioselectivity of N-substitution in bis-alkylation of 1,2,4-triazolo[1,5-a]benzimidazole-2-thione

Cyclization of the corresponding N-substituted 1,2-diaminobenzimidazoles with carbon disulfide in refluxing DMF leads to 3-methyl- and 3-benzyl-1,2,4-triazolo[1,5-a]benzimidazole-2-thiones. Based on the results of their S-alkylation, quantum chemical calculations by the density functional theory method, and 1D and 2D NMR spectroscopic studies, it was concluded that the bis-alkylation of N-unsubstituted 1,2,4-triazolo[1,5-a]benzimidazole-2-thione in the presence of a base proceeds with the formation of N(4)-derivatives of 2-alkylthio-1,2,4-triazolo[1,5-a]benzimidazole, rather than N(3)-derivatives as was believed earlier.

Recyclization of 9-bromocotarnine under the action of haloacylhetarenes. Synthesis and biological activity of the 4-heteroaroyl-9-bromo-1,2-dihydro-6-methoxy-7,8-methylenedioxy-3-benzazepines

Reaction of 9-bromocotarnine with heterocyclic α-halo ketones is accompanied by the expansion of the six-membered dihydropyridine ring to seven-membered dihydroazepine one and leads to previously unknown 4-heteroaroyl-9-bromo-3-methyl-1,2-dihydro-6-methoxy-7,8-methylenedioxy-3-benzazepines. It has been shown that some of the resulting compounds exhibit a significant antibacterial activity against Staphylococcus aureus and Escherichia coli. At the same time, the synthesized benzazepines have shown no significant protistocidal activity against Colpoda steinii and fungistatic activity against Penicillium italicum.

Synthesis and Antimicrobial and Protistocidal Activity of 1-(2-Aryloxyethyl- and 2-Halobenzyl)-3-(2-Hydroxyethyl)-2-Imino-1,3-Dihydrobenzimidazolines

New 1-(2-aryloxyethyl- and 2-halobenzyl)-3-(2-hydroxyethyl)-2-imino-1,3-dihydrobenzimidazoline hydrochlorides were synthesized via reactions of 1-(2-aryloxyethyl- and 2-halobenzyl)-2-aminobenzimidazoles with ethylenechlorohydrin. These compounds were shown to possess both bactericidal activity against some pathogenic Gram-positive and Gram-negative bacteria (Staphylococcus aureus, Escherichia coli) and pronounced protistocidal activity against the species Colpoda steinii.

Synthesis and Cyclization of 2-Amino- and 2-Methyl-Substituted 1,3-Diaminobenzimidazolium Salts

N-Amination of 1-amino(alkylamino, benzylidenamino)-substituted 2-amino- and 2-methylbenzimid-azoles with O-picrylhydroxylamine gave the respective 1,2,3-triamino- and 1,3-diamino-2-methylbenz-imidazolium salts, which cyclized upon treatment with acetic anhydride/K2CO3 into previously unreported derivatives of N-amino[1, 2, 4]triazolo[1,5-а]benzimidazoles and N-aminopyrazolo-[1,5-а]benzimidazoles. The presence of С-acetyl substituent in the formed pyrazolo[1,5-а]benz-imidazoles was interpreted by quantum-chemical calculations as resulting from acylation of the intermediate methylene base, not tricyclic system.