V. D. Ogorodnikov

Synthesis of ditopic ligands containing bis(1H-pyrazol-1-yl)-methane fragments

New approaches have been proposed for the synthesis of compounds containing two bis(1H-pyrazol-1-yl)methane fragments. Nucleophilic replacement of the halogen atoms in appropriate tetrabromo derivatives by pyrazoles in the superbasic system KOH-DMSO gave ditopic chelating ligands: 1,1,2,2-tetrakis(1H-pyrazol-1-yl)ethane, 1,4-bis[bis(1H-pyrazol-1-yl)methyl]benzene, and 1,4-bis[bis(3,5-dimethyl-1H-pyrazol-1-yl)methyl]benzene. 1,4-Bis[bis(1H-pyrazol-1-yl)methyl]benzene was also synthesized by reaction of 1H-pyrazole with terephthalaldehyde in the presence of thionyl chloride. 1,1,2,2-Tetrakis(1H-pyrazol-1-yl)ethane was converted into the corresponding tetraiodo and tetranitro derivatives.

1,3-Diiodo-5,5-dimethylhydantoin—An efficient reagent for iodination of aromatic compounds

Abstract1,3-Diiodo-5,5-dimethylhydantoin in organic solvents successfully iodinates alkylbenzenes, aromatic amines, and phenyl ethers. The reactivity of electrophilic iodine is controlled by acidity of the medium. Superelectrophilic iodine generated upon dissolution of 1,3-diiodo-5,5-dimethylhydantoin in sulfuric acid readily reacts with electron-deficient arenes at 0 to 20°C with formation of the corresponding iodo derivatives in good yields. The structure of electrophilic iodine species generated from 1,3-diiodo-5,5-dimethylhydantoin in sulfuric acid is discussed.

Superactivity and dual reactivity of the system N-iodosuccinimide-H2SO4 in the iodination of deactivated arenes

Dissolution of N-iodosuccinimide in sulfuric acid gives rise to electrophilic iodine-containing species which are capable of successfully iodinating aromatic compounds with electron-withdrawing substituents in the temperature range from 0 to 20°C. The iodination in sulfuric acid is effected by both protonated N-iodosuccinimide and IOS(O)(OH+)OH intermediate.

Synthesis of 1-ethylpyrazole-4-carbaldehydes, 1,1’-methylenebis(3,5-dimethylpyrazole-4-carbaldehyde), and Schiff bases derived therefrom

New pyrazole-containing aldehydes, 1-ethylpyrazole-4-carbaldehyde, 1-ethyl-3,5-dimethylpyrazole-4-carbaldehyde, and 1,1’-methylenebis(3,5-dimethylpyrazole-4-carbaldehyde), were synthesized by the Vilsmeier reaction. Their reactions with primary amines (aniline, hydrazine, ethylenediamine, p-phenylenediamine, benzidine) gave the corresponding Schiff bases.

Synthesis and oxidation of some azole-containing thioethers

Summary Pyrazole and benzotriazole-containing thioethers, namely 1,5-bis(3,5-dimethylpyrazol-1-yl)-3-thiapentane, 1,8-bis(3,5-dimethylpyrazol-1-yl)-3,6-dithiaoctane and 1,3-bis(1,2,3-benzotriazol-1-yl)-2-thiapropane were prepared and fully characterized. Oxidation of the pyrazole-containing thioether by hydrogen peroxide proceeds selectively to provide a sulfoxide or sulfone, depending on the amount of oxidant used. Oxidation of the benzotriazole derivative by hydrogen peroxide is not selective, and sulfoxide and sulfone form concurrently. Selenium dioxide-catalyzed oxidation of benzotriazole thioether by H2O2, however, proceeds selectively and yields sulfoxide only.

Synthesis of 1,8-di(pyrazol-1-yl)-3,6-dioxaoctane and its derivatives

From pyrazole, 3,5-dimethylpyrazole, and 1,8-dibromo-3,6-dioxaoctane in a superbasic medium KOH-DMSO the corresponding 1,8-di(pyrazol-1-yl)-3,6-dioxaoctanes were synthesized and converted into iodo-, nitro-, amino-, and formylderivatives.

Synthesis and Cytotoxicity of bis(pyrazol-1-yl)-Alkane Derivatives with Polymethylene Linkers and Related Mono- and Dipyrazolium Salts

Reactions of α,ω-dibromoalkanes with pyrazole and 3,5-dimethylpyrazole in superbasic medium of dimethyl sulfoxide – potassium hydroxide were used for the synthesis of bidentate ligands: bis(pyrazol-1-yl)alkanes and bis(3,5-dimethylpyrazol-1-yl)alkanes linked by alkyl chains containing between four and twelve methylene groups. Oxidative iodination of the obtained compounds with I2–HIO3–H2SO4 system in acetic acid provided diiodo derivatives: bis(4-iodopyrazol-1-yl)alkanes and bis(4-iodo-3,5-dimethylpyrazol-1-yl)alkanes. The obtained diiodo derivatives of pyrazole were further converted to mono- and dipyrazolium salts by alkylation of nitrogen atom at position 2 of the pyrazole rings with iodomethane, as well as with methyl triflate. These products are of interest as precursors to mesoionic N-heterocyclic carbene complexes. The cytotoxicity of the obtained compounds was studied against THP-1 monocytic leukemia cells.

Synthesis of New Bitopic Tetra(pyrazolyl)-Ligands with Neopentane and O-Xylene Backbones

Several new bitopic pyrazole-containing ligands were prepared from the corresponding pyrazoles and tetrahalogen or tetratosyloxy derivatives of o-xylene and neopentane in a superbasic medium (KOH-DMSO).

2,4,6,8-Tetraiodo-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione as a mild and convenient reagent for iodination of aromatic compounds

Abstract2,4,6,8-Tetraiodo-2,4,6,8-tetraazabicyclo[3.3.0]octane-3,7-dione (tetraiodoglycoluril) is a convenient reagent for preparative iodination of benzene, alkylbenzenes, polycyclic hydrocarbons, aromatic amines, and phenol ethers in organic solvents under mild conditions.

A new transformation of aminopyridines upon diazotization in acetonitrile with the formation of N-pyridinylacetamides

Diazotization of aminopyridines upon treatment with NaNO2 and H3PO4 in acetonitrile led to the formation of N-pyridinylacetamides. This reaction constitutes a convenient and general preparative method for the synthesis of 2-, 3-, and 4-N-pyridinylacetamides under mild conditions in good yields. The in situ oxidation of the thus obtained N-pyridinylacetamides with hydrogen peroxide gave good yields of pyridinylacetamide N-oxides.