Ekaterina A. Knyazeva

Recent Developments in the Synthesis and Applications of 1,2,5-Thia- and Selenadiazoles. A Review

1,2,5-Chalcogenadiazoles (oxa-, thia-, selena-, and telluradiazoles) have been known for many years. Their first representative, 2,1,3-benzothiadiazole (1), was discovered in 1889 by Hinsberg.1 Not...

Direct Exchange of Oxygen and Selenium Atoms in the 1,2,5-Oxadiazoles and 1,2,5-Selenadiazoles by Action of Sulfur Monochloride.

A short synthetic approach to fused 1,2,5-thiadiazoles from the corresponding 1,2,5-oxadiazoles and 1,2,5-selenadiazoles has been developed. Mono- and bis(1,2,5-thiadiazoles) were selectively obtained in high yields. The pathways for these novel reactions were discussed.

4,7-Dibromo-substituted 2,1,3-benzothia(selena,oxa)diazoles and [1, 2, 5]thia(selena)diazolo[3,4-c]pyridines as building blocks in solar cells components (microreview)

2,1,3-Benzothia(selena,oxa)diazoles and [1, 2, 5]thia(selena)diazolo[3,4-c]pyridines are important building blocks in dye-sensitized solar cells. This microreview summarizes synthesis of their dibromo derivatives and conversion to dye-sensitized solar cell components by cross-coupling reactions and copolymerization.

Nitro derivatives of 2,1,3-benzothiadiazole 1-oxides: synthesis, structural study, and NO release

A convenient one-pot synthesis of nitro derivatives of 2,1,3-benzothiadiazole 1-oxides by the reaction of o-nitroanilines with sulfur monochloride was developed. The structural features of 4-nitrobenzothiadiazole and its N-oxide were considered. High in vitro release of nitric oxide (69%) was found for a 6-nitro-2,1,3-benzothiadiazole sample by the Griess assay, which indicated good prospects for this class of compounds.

Safe Synthesis of 4,7-Dibromo[1,2,5]thiadiazolo[3,4-d]pyridazine and Its SNAr Reactions

A safe and efficient synthesis of 4,7-dibromo[1,2,5]thiadiazolo[3,4-d]pyridazine from the commercial diaminomaleonitrile is reported. Conditions for selective aromatic nucleophilic substitution of one or two bromine atoms by oxygen and nitrogen nucleophiles are found, whereas thiols formed the bis-derivatives only. Buchwald-Hartwig or Ullmann techniques are successful for incorporation of a weak nitrogen base, such as carbazole, into the [1,2,5]thiadiazolo[3,4-d]pyridazine core. The formation of rather stable S…η2-(N=N) bound chains in 4,7-bis(alkylthio)-[1,2,5]thiadiazolo[3,4-d]pyridines makes these compounds promising for the design of liquid crystals.

4,7-Dichloro[1,2,5]oxadiazolo[3,4-d]pyridazine 1-oxide

Dihalogenated derivatives of [1,2,5]chalcogenadiazolo[3,4-d]pyridazines are of interest as precursors for both photovoltaic materials and biologically active compounds. In this communication, 4,7-dichloro[1,2,5]oxadiazolo[3,4-d]pyridazine 1-oxide was prepared via the reaction of 3,6-dichloro-5-nitropyridazin-4-amine with oxidizing agents; the best yield of the target compound was achieved in the reaction with (diacetoxyiodo)benzene in benzene by heating at reflux for two hours. The structure of the newly synthesized compound was established by means of 13C-NMR and IR spectroscopy, mass-spectrometry and elemental analysis.

Suzuki cross-coupling reactions of 4,7-dibromo[1, 2, 5]selenadiazolo[3,4-c]pyridine – a path to new solar cell components

A study of Suzuki cross-coupling reactions of 4,7-dibromo[1, 2, 5]selenadiazolo[3,4-c]pyridine resulted in the first synthesis of photosensitizers on the basis of [1, 2, 5]selenadiazolo[3,4-c]pyridine system. Optical and electrochemical properties of the obtained dyes were studied and were found to meet the requirements for photosensitizers that can be used for the creation of organic solar cells.

Synthesis of 4-substituted 3-chloro-1,2,5-thiadiazoles from monosubstituted glyoximes

One-pot synthesis of 3-chloro-1,2,5-thiadiazoles from monosubstituted glyoximes and sulfur monochloride was developed.

Synthesis of 4,8-dihydro-7H-[1,2]dithiolo[3,4-b][1,2,5]oxadiazolo-[3,4-e]pyrazine-7-thione as a new heterocyclic system

Sulfur monochloride and its complexes with tertiary amines are important sources of sulfur in the synthesis of novel heterocyclic systems.1—4 This available and inex pensive reagent allows such transformations to be com pleted in one step.5 With 3,4 diaminofurazan and 4 ami no 3 nitrofurazan as examples, we have discovered an ear lier unknown transformation of the 1,2,5 oxadiazole ring into the 1,2,5 thiadiazole ring under the action of sulfur monochloride.6,7 By analyzing the results obtained, we concluded that the furazan ring should contain an NH substituent for this transformation to be successful. For a further study of reactions of 1,2,5 oxadiazoles with sulfur mono chloride, we used 3,4 bis(alkyl amino)furazans 1 (R = Et, Pri) as new starting materials. Earlier, we have found that the N ethyl8 and N isopropyl9 groups can also interact with S2Cl2, so the reaction pathway for com pounds 1 was unpredictable. It turned out that 3,4 bis(alkylamino)furazans 1 (R = Et (a), Pri (b)) both react with S2Cl2 in hot dimethyl formamide (100—105 C) over 2 h. The reaction with bis(ethylamino) derivative 1a gave an inseparable mixture of products, from which we failed to isolate individual compounds. The reaction with 3,4 bis(isopropylamino) furazan 1b yielded a product containing only one isopro pyl group (NMR data). Data from elemental analysis, 1H and 13C NMR spectroscopy, IR spectroscopy, and mass spectrometry suggest two possible tricyclic structures for this product: oxadiazolodithiolopyrazinethione 2 or thia diazolodithiolopyrazinone 3 (Scheme 1). X ray diffraction provided conclusive evidence for structure 2 (Fig. 1, Table 1). The formation of product 2 can be explained by a trans formation9,10 of the N isopropyl group of furazan 1b into R = Et (a), Pri (b)