The photolysis of 1-(4,5-dihydro-1H-imidazol-2-yl)benzotriazole

1-(4,5-Dihydro-1H-imidazolo-2-yl)benzotriazole was photolyzed at 254 nm yielding 1,2-dihydro-4H-imidazo-[1,2-a]benzimidazole.     

Reactions of vinyl 2,3-epoxypropyl ethers with 4,5-dihydro-1H-pyrazoles

Reactions of vinyl 2,3-epoxypropyl ether and 2-(vinyloxy)ethyl 2,3-epoxypropyl ether with 4,5-dihydro-1H-pyrazoles give, respectively, 3-vinyloxy-1-(4,5-dihydro-1H-pyrazol-1-yl)propan-2-ols and 3-(2-vinyloxyethoxy)-1-(4,5-dihydro-1H-pyrazol-1-yl)propan-2-ols in 70–91% yield.     

Synthesis and Characterization of Novel 2-(1,2,3-Triazol-4-yl)-4,5-dihydro-1H-pyrazol-1-yl)thiazoles and 2-(4,5-Dihydro-1H-pyrazol-1-yl)-4-(1H-1,2,3-triazol-4-yl)thiazoles

Reactions of 1-(5-methyl)-1H-1,2,3-triazol-4-yl)ethan-1-ones and benzaldehydes in ethanol under basic conditions gave the corresponding chalcones. Reactions of the chalcones combined with thiosemicarbazide in dry ethanol containing sodium hydroxide afforded the corresponding pyrazolin-N-thioamides. Reactions of the synthesized pyrazolin-N-thioamides and several ketones (namely, ethyl 2-chloro-3-oxobutanoate, 2-bromoacetylbenzofuran, and hydrazonoyl chloride) gave the corresponding novel 2-(1,2,3-triazol-4-yl)-4,5-dihydro-1H-pyrazol-1-yl)thiazoles in high yields (77–90%). Additionally, 2-(4,5-dihydro-1H-pyrazol-1-yl)-4-(1H-1,2,3-triazol-4-yl)thiazoles were obtained in high yields (84–87%) from reactions with N-pyrazoline-thioamides and 4-bromoacetyl-1,2,3-triazoles under basic conditions. The structures of six of the newly synthesized heterocycles were confirmed by X-ray crystallography.     

Synthesis of 3-(pyridine-2-yl)-4,5-dihydro-1H-pyrazole-1-thiocarboxamides and their copper(II) complexes

New organic ligands 3-(pyridine-2-yl)-4,5-dihydro-1H-pyrazole-1-thiocarboxamides (L) have been synthesized by a two or three step reaction sequence starting from substituted benzaldehydes and 2-acetyl pyridine. Copper(II) complexes with LCuCl₂ composition were obtained by the reactions of these ligands with CuCl₂·2H₂O. The crystal structure of two synthesized complexes has been determined by X-ray analysis. Copper atoms located in a strongly distorted square piramidal environment and coordinated by pyrazoline and pyridine nitrogen atoms, thiocarbamoyl sulfur atom and two chloride-anions. All complexes undergo reversible or quasi-reversible electrochemical reduction at 0.45–0.28 V with the formation of Cu(I) containing intermediates. The cytotoxicity of copper containing complexes, comparable to cisplatin and doxorubicin, was demonstrated using cancer cell lines MCF-7, A549 and HEK293.     

Experimental, theoretical and biological activity study on 1-(4,5-dihydro-3-arylpyrazol-1-yl)-2-(1H-1,2,4-triazol-1-yl)-ethanone

Four compounds have been synthesized and characterized by¹H NMR spectroscopy and elemental analyses, among which 1-(4,5-dihydro-3-phenyl-pyrazol-1-yl)-2-(1H-1,2,4-triazol-1-yl)ethanone 3a was further confirmed by X-ray crystallographic analysis. The biological activities of these compounds were tested, with the result that they displayed moderate fungicidal activities. In addition, a MO calculations using density functional theory (DFT) at B3LYP/6-31G^* level have also been carried out, and the structure–activity relationships for these compounds are discussed.     

Synthesis of 3-(3-Alkyl-5-thioxo-1H-4,5-dihydro-1,2,4-triazol-4-yl)aminocarbonylchromones

A series of 3-(3-alkyl-5-thioxo-1H-4,5-dihydro-1,2,4-triazol-4-yl)aminocarbonylchromones has been prepared by oxidation of 3-formylchromone with Jones' reagent followed by reaction with 3-alkyl-4-amino-4,5-dihydro-1,2,4-triazole-5(1H)-thione in the presence of POCl³. The structures of the compounds were confirmed by IR, LC-MS, and ¹H NMR spectra and elemental analyses.     

Synthesis of 3-substituted pyrazoles by oxidative dehydrogenation of 4,5-dihydro-3H-pyrazoles

Russian Journal of Organic Chemistry -     

Recyclization of isopropyl 2-(1-aryl-4,5-dioxo-2-phenyl-4,5-dihydro-1H-pyrrol-3-yl)-2-oxoacetates by the action of thiourea

Russian Journal of Organic Chemistry -     

Synthesis of 4,5-dichloro-1-(4,5-dichloropyridazin-3-yl)pyridazin-6-one

This paper presents the synthesis of 4,5-dichloro-1-(4,5-dichloropyridazin-3-yl)pyridazin-6-one from 4,5-dichloropyridazin-6-one.     

From Levulinic Acid to Biheterocycles: Synthesis of 1-[(5-Hydroxy-5-trifluoromethyl-3-substituted-4,5-dihydro-1H-pyrazol-1-yl)-3-(5-trifluoromethyl-1H-pyrazol-3-yl)propan-1-ones

We develop an efficient method to synthesize novel propionyl-spaced bisheterocyclic compounds. It entails cyclocondensation of 3-(5-trifluoromethyl-1H-pyrazol-3-yl)propanoyl hydrazide obtained from levulinic acid, with 1,1,1-trifluoro-4-methoxy-3-alken-2-ones proceeding regiospecifically to 1-[(5-trifluoromethyl-5-hydroxy-3-substituted-4,5-dihydro-1H-pyrazol-1-yl)-3-(5-trifluoromethyl-1H-pyrazol-3-yl)propan-1-one derivatives.     

Thermolysis of hexasubstituted-4,5-dihydro-3H-pyrazoles: Synthesis of 1-alkoxy- and 1-acetoxy-1,2,2,3,3-pentasubstituted-cyclopropanes

A series of 5-alkoxy- and 5-acetoxy-4,4-dimethyl-3,3,5-trisubstituted-4,5-dihydro-3H-pyrazoles 2a-f (hexasubstituted pyrazolines) was synthesized by oxidation of the corresponding 3,4-dihydro-2H-pyrazoles with lead tetraacetate in the appropriate solvents. The 5-acetoxy compounds were produced when the oxidations were carried out in methylene chloride. Oxidation with lead tetraacetate in dry alcoholic solvents resulted in the formation of the 5-alkoxy derivatives as the major products. Thermolysis of the hexasubstituted-4,5-dihydro-3H-pyrazoles 2a-f in cyclohexane or as the melt at high temperature yielded the 1-alkoxy- and 1-acetoxy-1,2,2,3,3-pentasubstituted cyclopropanes 3a-f in good yields. Trace amounts of alkene products were formed in several reactions. No products attributable to cycloreversion pathways were detected. The product distributions were consistent with extrusion of nitrogen gas from 2a-f to yield the singlet 1,3-diradical, closure of which resulted in cyclopropane formation with partial retention of stereochemistry.     

A novel synthesis of 5-perfluorophenyl 4,5-dihydro-1H-pyrazoles in THF or water

5-Perfluorophenyl 4,5-dihydro-1H-pyrazoles were synthesized from 1,3-dipolar cycloaddition reaction of perfluorobenyl 2,4,6-triisopropylbenzenesulfonylhydrazone and α,β-unsaturated carbonyl compounds or acrylonitrile in THF or water. It was worthy to note that better results were obtained when water was employed as the solvent, which was considered as an effective, economic and environmentally friendly method to synthesize these pyrazole derivatives.