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The reaction of 3,5-dimethyl-4-formylpyrazoles, bearing various substituents at N-1 atom, with propane-1,3-diselenol and 2-hydroxypropane-1,3-diselenol in the presence of ТМSCl proceeds without heating to chemoselectively give hitherto unknown 2-(pyrazol-4-yl)-1,3-diselenane hydrochlorides in high yields. The latter are easily transformed to the corresponding free bases—2-(pyrazol-4-yl)-1,3-diselenanes. The 15N chemical shifts of the pyrazole ring in 2-(pyrazol-4-yl)-1,3-diselenanes obtained by 2D HMBC-gp (15N-1H) technique are indicative of the N-2 atom protonation in hydrochlorides.

Simple grinding of the title substrates with Al2O3 results in highly selective ethynylation of the pyrrole rings.

Trialkylamines react with acyl- and cyanoacetylenes in the presence of water (90–100 °C, 37–43 h) to give functionalized N , N -dialkyl-vinylamines, the products of N-dealkylation of the starting amines, in 22–44% yields.

The reaction of 3,5-dimethyl-4-formylpyrazoles, bearing various substituents at N-1 atom, with propane-1,3-diselenol and 2-hydroxypropane-1,3-diselenol in the presence of ТМSCl proceeds without heating to chemoselectively give hitherto unknown 2-(pyrazol-4-yl)-1,3-diselenane hydrochlorides in high yields. The latter are easily transformed to the corresponding free bases—2-(pyrazol-4-yl)-1,3-diselenanes. The 15N chemical shifts of the pyrazole ring in 2-(pyrazol-4-yl)-1,3-diselenanes obtained by 2D HMBC-gp (15N-1H) technique are indicative of the N-2 atom protonation in hydrochlorides.

The reaction of chloroacetyl chloride with 1,2-dichloroethene in the presence of AlCl3 unexpectedly led to the formation of (E)-1,1,4-trichlorobut-3-en-2-one whose structure was proved by 1H and 13C NMR, IR, and mass spectra and independent synthesis. A probable reaction scheme was proposed, which involves transformation of initially formed 1,2,4-trichloro-3-oxobutan-2-yl cation by the action of AlCl3. The high reactivity of the vinylic halogen atom in (E)-1,1,4-trichlorobut-3-en-2-one was demonstrated by its reactions with nitrogen-centered nucleophiles (triethylamine, aniline, 3,5-dimethyl-1H-pyrazole) and sodium sulfide. These reactions involved only the C-Cl bond in the vinyl fragment and afforded (4,4-dichloro-3-oxobut-2-en-1-yl)triethylammonium chloride, 1,1-dichloro-4-phenylaminobut-3-en-2-one, 1-(4,4-dichloro-3-oxobut-2-en-1-yl)-3,5-dimethyl-1H-pyrazole, and 4,4′-thiobis(1,1-dichlorobut-3-en-2-one), respectively. The reaction of 1,1,4-trichlorobut-3-en-2-one with benzylhydrazine gave a mixture of 1,3- and 1,5-disubstituted pyrazoles.

Regioselective heterocyclization of alkyl 2-chloro-and 2,2-dichlorovinyl ketones with 1,1-dialkyl-hydrazines to 1,3-dialkyl-1H-pyrazoles and 1,3-dialkyl-5-chloro-1H-pyrazoles involves intermediate formation of the corresponding dialkylhydrazones. Fragmentation pattern of chlorine-containing pyrazoles, 3-chloromethyl-1-methyl-1H-pyrazole and 5-chloro-1-methyl-3-propyl-1H-pyrazole, depends on the position of the halogen atom.

Reactions of 1,2-dihaloethanes with chalcogenide anions generated from elemental chalcogens and dimethylchalcogens were performed in the hydrazine hydrate-KOH system. The use of anions Se x 2− and Te x 2− (x = 1−4) resulted in ethylene evolution and chalcogen regeneration (or in increased x value in an anion). Oligomers of Thiokol type formed only in the reaction of the 1,2-dichloroethane with a mixture of potassium disulfide and diselenide. The reductive cleavage of oligomers obtained in the hydrazine hydrate-KOH system followed by methylation led to the formation of 1,2-bis(methylthio)ethane, 1-methylseleno-2-methylthioethane, and 1,2-bis(methylseleno)ethane. The features of substitution with chalcogenide anions in vicinal dihalides are discussed. Mass spectra of compounds obtained were measured and analyzed.