S. V. Shishkina

Cyclocondensation of 2-Aminobenzimidazole with Dimedone and Its Arylidene Derivatives

The reactions of 2-aminobenzimidazole with substituted benzaldehydes and dimedone, 2-arylidene derivatives of dimedone, 9-arylhexahydro-1H-xanthene-1,8(2H)-diones and also with dimedone and DMF have been studied. The direction of formation of the pyrimidine ring has been established and discussed. An X-ray structural investigation of 2,2-dimethyl-2,3-dihydrobenzimidazo[1,2-a]quinazolin-4(1H)-one has been carried out.

Cyclobutane-derived diamines: synthesis and molecular structure.

Cyclobutane diamines (i.e., cis- and trans-1,3-diaminocyclobutane, 6-amino-3-azaspiro[3.3]heptane, and 3,6-diaminospiro[3.3]heptane) are considered as promising sterically constrained diamine building blocks for drug discovery. An approach to the syntheses of their Boc-monoprotected derivatives has been developed aimed at the preparation of multigram amounts of the compounds. These novel synthetic schemes exploit classical malonate alkylation chemistry for the construction of cyclobutane rings. The conformational preferences of the cyclobutane diamine derivatives have been evaluated by X-ray diffraction and compared with the literature data on sterically constrained diamines, which are among the constituents of commercially available drugs.

An entry into hexahydro-2H-thieno[2,3-c]pyrrole 1,1-dioxide derivatives.

Hexahydro-2H-thieno[2,3-c]pyrrole is proposed as a low molecular weight polar scaffold to construct compound libraries used in the search for new drugs. Practical syntheses of derivatives of this bicyclic scaffold were developed, based on [3 + 2] cycloaddition of the ylide generated from N-benzyl-1-methoxy-N-((trimethylsilyl)methyl)methanamine and 4-substituted 2,3-dihydrothiophene 1,1-dioxides. All of the 3-substituted hexahydro-2H-thieno[2,3-c]pyrrole 1,1-dioxide derivatives were obtained as single diastereomers. Conformational properties of the hexahydro-2H-thieno[2,3-c]pyrrole 1,1-dioxide derivatives were explored using X-ray diffraction studies. The potential of the scaffold to generate libraries of 3D-shaped molecules was demonstrated.

Investigation of the products of interaction of cyclic diketones with nitrogen-containing 1,4-binucleophiles

The interaction of arylbis(5,5-dimethylcyclohexane-1,3-dion-2-yl)methanes with o-phenylenediamine and o-aminophenol leads to the preparation of 3,3-dimethyl-11-aryl-2,3,4,5,10,11-hexahydrobenzo[b,e]-1,4-diazepin-1-ones and 3,3,6,6-tetramethyl-9-aryl-10-(2-hydroxyphenyl)-2,4,5,7,9-decahydroacridine-1,8-diones respectively. A one-pot method is proposed for the synthesis of derivatives of hexahydrodibenzo[b,e]-1,4-diazepin-1-ones. The structure of the first member of this series was confirmed by X-ray diffraction analysis.

A new one-step synthesis of 1,2,4 -triazino [2,3 -c ]-quinazolines

A new and efficient one-step protocol for the synthesis of 3-substituted 2H-l,2,4-triazino[2,3-c]quinazolin-2-ones (5) was developed starting from 4-hydrazinoquinazoline (1) and α-ketocarboxylic acids and their esters. Corresponding hydrazones (2a,c and 3a,c,e) were isolated as intermediate products. Further cyclocondensation followed by acid-catalyzed Dimroth rearrangement resulted in the title derivatives 5.

Cascade cyclization of 3(5)-aminopyrazoles with aromatic aldehydes and cyclohexanediones

Three-component condensation of 5(3)-amino-3(5)-methylpyrazole with aromatic aldehydes and 1,3-cyclohexanedione afforded mixtures of 3-methyl-4-aryl-2,4,6,7,8,9-hexa hydro-5H-pyrazolo[3,4-b]quinolin-5-ones and 2-methyl-9-aryl-5,6,7,9-tetrahydro pyrazolo[5,1-b]quinazolin-8(4H)-ones. The reaction of 3-aminopyrazolo-4-carbonitrile and ethyl 3-aminopyrazolo-4-carboxylate with aldehydes and cyclo hexanedione or dimedome is regioselective and leads to the formation of partially hydrogenated pyrazolo [5,1-b]quinazolin-8-one systems. In all compounds the dihydroazine ring exists in the enamine tautomeric form.

Reaction of 2-hetarylacetonitriles with ethyl 2-alkylsulfanyl-4-chloro-5-pyrimidinecarboxylates. Synthesis of new condensed pyrimidines

Abstract Reactions of 2-hetarylacetonitriles 1 with ethyl 2-alkylsulfanyl-4-chloro-5-pyrimidinecarboxylates 4 were studied. The interaction of pyridine, benzimidazole and benzothiazole derivatives 1a–d affords a series of new condensed pyridopyrimidines 5–7 . In the case of benzoxazole- and 4-arylthiazole derivatives 1e–h ethyl 4-[(2-hetaryl)-cyano-methyl]-2-alkylsulfanylpyrimidine-5-carboxylates 9a–f were formed. Reactions of quinazoline derivatives 1i,k afford stable intermediates 9h,i which formed the cyclic compound 12 of angular structure in the presence of potash. The influence of the basicity of heterocycles and of steric factors on the intramolecular acylation reaction was studied.

Synthesis of partially hydrogenated pyrazolo[3,4-b]quinolinones by condensation of 3-amino-5-methylpyrazole with aromatic aldehydes and dimedone

Cyclocondensation of 3-amino-5-methylpyrazole with 2-arylmethylidene-5,5-dimethylcyclohexane-1,3-diones or 9-aryl-3,3,6,6-tetramethyl-2,3,4,5,6,7,8,9-octahydro-1H-xanthene-1,8-diones, as well as with synthetic precursors of the latter (para-substituted benzaldehydes and dimedone), in dimethylformamide or methanol gives the corresponding 4-aryl-3,7,7-trimethyl-2,4,6,7,8,9-hexahydropyrazolo[3,4-b]quinolin-5-ones. The structure of 4-(4-methoxyphenyl)-3,7,7-trimethyl-2,4,6,7,8,9-hexahydropyrazolo[3,4-b]quinolin-5-one was proved by the X-ray diffraction data.

Reaction of thiosemicarbazide with N-cyanoguanidine : synthesis of 3,5-diamino-1-thiocarbamoyl- and 3,5-diamino-1-thiazol-2-yl-1,2,4-triazoles

The reaction of thiosemicarbazide with N-cyanoguanidine in an acidic medium afforded 3,5-diamino-1-thiocarbamoyl-1,2,4-triazole, whose condensation with α-halo ketones gave 3,5-diamino-1-thiazol-2-yl-1,2,4-triazoles 7a–d. The latter were also prepared by the independent synthesis from 2-hydrazinothiazoles and N-cyanoguanidine. Acylation of compounds 7a,d under mild conditions and their condensation with aldehydes occur at the C(3′)NH2group. The structure of aroyl derivative 11c was established by X-ray diffraction. Acylation of diaminothiazolyltriazole 7a in boiling Ac2O afforded 3,5-diacetylamino-1-(4-phenylthiazol-2-yl)-1,2,4-triazole. Hydrogenation of arylidene derivatives 14b,c and aroyl derivative 11c gave the corresponding benzylaminotriazoles 15a,b.

Dibutylphosphinoylmethyloxythiacalix[4]arenes. Synthesis, structure, americium, europium and technetium extraction

A series of thiacalix[4]arenes bearing one, two or four chelating dibutylphopshinoylmethoxy groups have been synthesised and studied in the context of this paper. The synthesis consisted of precise Williamson alkylation of thiacalixarene tetrols with tosylate of dibutylhydroxymethyl phosphine oxide in the presence of alkali metal carbonates or sodium hydride. Stereochemical yield of the reaction (cone or 1,3-alternate conformer) depends on the nature of alkali metal. Small-sized ‘hard’ sodium cation organises the macrocyclic platform in the cone conformation, but larger and ‘soft’ potassium and cesium cations stabilise the macrocycle in the 1,3-alternate conformation. All synthesised compounds (except monophosphine monoxide) possess either moderate or high extraction ability towards pertechnetate ion. The cone-shaped thiacalix[4]arene tetraphosphine tetraoxide due to cooperative (macrocyclic) effect of eight oxygen atoms of the phosphinoylmetoxy-binding groups effectively extract spherical americium, europium cations due to cooperative (macrocyclic) effect of eight oxygen atoms of the phosphinoylmetoxy-binding groups. The extraction ability is very similar to that of calix[5]arene pentaphosphine pentaoxide existing in the cone conformation.