M. A. Ezhikova

Imidazolyl derivative of chitosan with high substitution degree: Synthesis, characterization and sorption properties.

A method of synthesis of chitosan imidazolyl derivative - N-(5-methyl-4-imidazolyl)methylchitosan (IM-chitosan) with high degree of substitution (DS) via reaction with 5-methyl-4-imidazolylmethanol has been developed. This method enables one to obtain polymers with the DS up to 1.35 with simultaneous cross-linkage of the matrix. The chemical structure of the obtained IM-chitosan was characterized by FT-IR, (13)C and (15)N NMR spectroscopies. It was shown that cross-linkage of IM-chitosans occurred due to formation of N-glucoside derivatives. Sorption capacities of IM-chitosans toward transition metal ions have an extremal dependence on DS, which is less pronounced for Ag(I) ions in comparison with Cu(II) and Ni(II) ions. The decrease of sorption capacities for derivatives with DS 0.5-1.0 is attributed to steric hindrances for ion-binding due to increased stiffness of the polymer matrix at high DS as a result of cross-linking. Sorption capacities of IM-chitosans toward noble metal ions in 0.1M HCl gradually increase with DS, since higher swelling polymers in acidic media eliminates negative effect of cross-linking on availability of sorption sites.

Preparation of a sorbent for metal ions based on N-(5-methylimidazol-4-ylmethyl) chitosan with medium degree of substitution

A procedure was developed for preparing a heterocycle-containing chelating amino polymer, N-(5-methylimidazol-4-ylmethyl) chitosan, by polymer-analogous transformations of chitosan in reaction with 4-chloromethyl-5-methylimidazole. The procedure allows synthesis of the polymer with the degree of substitution of up to 0.8, with simultaneous formation of the cross-linked structure. The structure of the polymers prepared was proved by IR and 13C NMR spectroscopy. The ability of N-(5-methylimidazol-4-ylmethyl) chitosan with the degree of substitution of 0.54 to sorb Cu2+ and Ni2+ ions was evaluated. According to the sorption isotherms, the sorption capacity of this derivative exceeds that of the unmodifi ed polymer by a factor of 5.

Synthesis of 1-substituted 2-azaspiro[4.5]deca-6,9-dien-8-ones and 2-azaspiro[4.5]deca-1,6,9-trien-8-ones by condensation of 2,6-dimethylphenol with isobutyraldehyde and nitriles

Abstract1-Substituted 3,3,7,9-tetramethyl-2-azaspiro[4.5]deca-6,9-dien-8-ones and 3,3,7,9-tetramethyl-2-azaspiro[4.5]deca-1,6,9-trien-8-ones were synthesized by three-component condensation of 2,6-dimethylphenol with isobutyraldehyde and nitriles in concentrated sulfuric acid.

Reactions of zinc enolates derived from 1-aryl-2,2-di-bromoalkanones with 2-acyl-3H-benzo[f]chromen-3-ones, 6-bromo-2-oxochromene-3-carboxamides, and 3-oxo-3H-benzo-[f]chromene-2-carboxamides

Zinc enolates derived from substituted 1-aryl-2,2-dibromoalkanones reacted with 2-acyl-3H-benzo-[f]chromen-3-ones to give 1-alkyl-1-aroyl-1a-acyl-1a, 9c-dihydro-1H-3-oxacyclopropa[c]phenanthren-2-ones which were formed as a single stereoisomer. Reactions of the same zinc enolates with 6-bromo-2-oxo-chromene-3-carboxamides (piperidides and morpholides) afforded 1-aroyl-6-bromo-1-alkyl-1a-piperidino-(morpholino)carbonyl-1a,7b-dihydrocyclopropa[c]chromen-2-ones with high stereoselectivity. Likewise, 1-benzoyl-1-methyl-1a-morpholinocarbonyl-1a, 9c-dihydro-1H-3-oxacyclopropa[c]phenanthren-2-one was obtained by reac-tion with 3-oxo-3H-benzo[f]chromene-2-carboxylic acid morpholide.

The reactions of 2-ethoxymethylidene-3-oxo esters and their analogues with 5-aminotetrazole as a way to novel azaheterocycles.

Summary The interaction of 2-ethoxymethylidene-3-oxo esters and their analogues with 5-aminotetrazole is an efficient synthetic approach to novel azaheterocycles. 2-Ethoxymethylidene-3-oxo esters bearing alkyl substituents react with 5-aminotetrazole to form ethyl 2-azido-4-alkylpyrimidine-5-carboxylates which are capable of subsequent nucleophilic substitution. The use of diethyl 2-ethoxymethylidenemalonate in this reaction resulted in ethyl 7-hydroxytetrazolo[1,5-a]pyrimidine-6-carboxylate, while ethyl 2-ethoxymethylidenecyanoacetate yielded 5-[2,6-diamino-3,5-bis(ethoxycarbonyl)pyridinium-1-yl]tetrazol-1-ide through an alternative pathway. Ethyl 2-benzoyl-3-ethoxyprop-2-enoate reacted with 5-aminotetrazole by two reaction routes to form ethyl 2-benzoyl-3-(1H-tetrazol-5-ylamino)prop-2-enoate and ethyl 7-(1-ethoxy-1,3-dioxo-3-phenylpropan-2-yl)-5-phenyl-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate.

Synthesis of 5-(het)aryl- and 4,5-di(het)aryl-2-(thio)morpholinopyrimidines from 2-chloropyrimidine via SNH and cross-coupling reactions

It has been shown that various combinations of nucleophilic aromatic substitution of hydrogen (SNH), SNipso and the microwave-assisted Suzuki cross-coupling reactions are a versatile method for the synthesis of 5-(het)aryl-2-(thio)morpholinopyrimidine and 4,5-di(het)aryl-2-(thio)morpholinopyrimidine derivatives. All synthesized pyrimidines were found to be active in micromolar concentrations in vitro against Mycobacterium tuberculosis H37Rv.

Diastereoselective Acylation of Racemic Heterocyclic Amines with N-Tosyl-(S)-Prolyl Chloride and its Structural Analogs

A comparative study on the kinetic resolution of racemic amines (2,3-dihydro-4H-1,4-benzoxazine and 1,2,3,4-tetrahydroquinoline derivatives) via diastereoselective acylation with N-tosyl-(S)-prolyl chloride and its structural analogs was performed. The effect of resolving agent structure on the stereoselectivity of heterocyclic amine acylation was examined. The highest stereoselectivity was achieved in the case of acylation with acyl chlorides bearing a conformationally restricted pyrrolidine ring and an aromatic substituent in the protecting group at the nitrogen atom.

New Opportunities for the Synthesis of Quinoxaline-Substituted Heterocyclic and Aryl Moieties

6.7-Difluoroquinoxaline (I) reacted with dimedone, indandione, and 3-methyl-1-phenylpyrazol-5-one in DMSO solution in the presence of acid to form mono-substituted products IIa – c. Heating I with resorcinol in EtOH in the presence of acid gave resorcinol derivative IId. 6.7-Difluoroquinoxaline in the presence of base reacted with 3-methyl-1-phenylmethylpyrazol-5-one to form dipyrazolylmethane III and tetrapyrazolylethane derivative IV. Heating products IIa – c with N-methylpiperazine produced 7-methylpiperazine derivatives Va – c of 2-substituted quinoxalines.

Reaction of 2-(ethoxymethylidene)-3-oxo carboxylic acid esters with tetrazol-5-amine

Abstract2-(Ethoxymethylidene)-3-oxo carboxylic acid esters reacted with tetrazol-5-amine to give ethyl 4-alkyl-2-azidopyrimidine-5-carboxylates capable of undergoing subsequent nucleophilic substitution of hydrogen on C6 or azido group. The reaction of ethyl 2-benzoyl-3-ethoxyprop-2-enoate with tetrazol-5-amine was accompanied by partial decomposition to afford a mixture of ethyl 3-oxo-3-phenylpropanoate and ethyl 7-(1-ethoxy-1,3-dioxo-3-phenylpropan-2-yl)-5-phenyl-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate. Ethyl 7-hydroxytetrazolo[1,5-a]pyrimidine-6-carboxylate was formed as a result of cyclization of diethyl 2-(ethoxymethylidene)propanedioate with tetrazol-5-amine.

Synthesis of trans,trans-2,3,4-trisubstituted chromans from 3-nitro-2Н-chromenes and enamines of acetoacetic ester and acetylacetone. A new type of configurationally stable atropisomers

Enamines of acetoacetic ester and acetylacetone added at the activated double bond of 2-R1-3-nitro-2Н-chromenes (R1 = CF3, CCl3, Ph) with their central α-С atoms, forming trans,trans-2,3,4-trisubstituted chromans. The adducts obtained from acetylacetone enamines represented mixtures of comparable amounts of configurationally stable atropisomers, the formation of which was connected with hindered rotation around the C(sp3)–C(sp2) bond. A reaction with enamines of acetoacetic ester led practically exclusively to a single anti atropisomer.