Tandem carbon-carbon bond-forming radical addition-cyclization reaction of oxime ether and hydrazone

The novel tandem radical addition-cyclization of oxime ethers and hydrazones intramolecularly connected with the alpha,beta-unsaturated carbonyl group is described. The radical reaction of oxime ethers 1, 2, and 4 connected with acryloyl and methacryloyl moieties proceeded smoothly to give the heterocycles via a tandem C-C bond-forming process. The tandem reaction of hydrazone 5 took place in the presence of Zn(OTf)(2) as a Lewis acid to give the trans-cyclic product 17 without the formation of the cis-isomer. The diastereoselective radical addition-cyclization reaction of chiral oxime ether 19 was also studied. The tandem reaction of 19 proceeded smoothly even in aqueous media, providing the novel method for asymmetric synthesis of gamma-butyrolactones and beta-amino acid derivatives.     

New synthesis of pyrazole and isoxazole derivatives

A convenient synthesis of 5-aryl-1-phenylpyrazoles and 5-arylisoxazoles, from readily available ketimine 1 dimethylformamide dimethylacetal and phenylhydrazine or hydroxylamine, is described.     

Cyclization of chalcones to isoxazole and pyrazole derivatives

A series of pyrazole and isoxazole derivatives were obtained by the condensation of the chalcones with hydrazine, phenylhydrazine, and hydroxylamine. All compounds were characterized using NMR, IR, and MS techniques.     

A convenient synthesis of cis-restricted combretastatin analogues with pyrazole and isoxazole cores

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Synthesis of pyrazole-3-carboxylates and pyrazole-1,5-dicarboxylates by one-pot cyclization of hydrazone dianions with diethyl oxalate

The one-pot cyclization of hydrazone dianions with diethyl oxalate allows a convenient synthesis of pyrazole-3-carboxylates and pyrazole-1,5-dicarboxylates.     

Syntheses of 1,2,4-oxadiazole substituted pyrazole,isoxazole and pyrimidine heterocycles

Syntheses of two series of heterocyclic compounds having 1,2,4-oxadiazole-, together with pyrazole-, isoxazole- or pyrimidine-rings which have similar structures are reported. The mechanisms of the reactions are discussed.     

The reaction of allyldialkyltelluronium bromides with anilines

Allyldialkyltelluronium bromides were treated with aromatic amines in 1,2-dichloroethane, readily giving allyl aryl amines in excellent yields.     

beta-Diketone, pyrazole and isoxazole derivatives with polar groups: Liquid crystalline and non-linear optical properties

The liquid crystalline behaviour of 1-(4-n-decyloxyphenyl)-3-(4-X-phenyl)propan-1,3-diones and their pyrazole and isoxazole derivatives has been studied by optical microscopy, DSC and X-ray techniques. The 4-substituents (X) were chosen to include a range of different polar and non-polar substituents: H, OCH3, Cl, Br and CN. A monotropic SA phase is observed for the beta-diketone derivative in which X CN and this is the first example of this phase found in a 1,3-diphenylpropan-1,3-dione derivative. The majority of the pyrazole and isoxazole compounds show SA phases. As regards the cyano-substituted compounds, X-ray diffraction studies on the mesophase show that the layer spacing is consistent with a partial bilayer SA mesophase. The first hyperpolarizabilities of the cyano-derivatives due to their push-pull structure have been measured by the EFISH method. Values for these compounds were found to be comparable to those for other conjugated CH3O-pi-CN systems.     

Synthesis and bioactivity of novel pyrazole oxime derivatives containing oxazole ring

A series of novel pyrazole oxime derivatives containing oxazole ring were designed and synthesized. The title compounds were structurally confirmed by 1H NMR, 13C NMR spectra and elemental analyses. Preliminary bioassay results showed that some of the title compounds displayed promising fungicidal activity besides insecticidal and acaricidal activity. Particularly, compound 8c exhibited potent fungicidal activity against cucumber Pseudoperonospora cubensis beyond good insecticidal activity against Aphis craccivora and Nilaparvata lugens.     

Generation of sec-thioamide dianions and their regioselective reaction with electrophiles.

The enolates of sec-thioamides $\text{8}$, which are generated by three different methods (scheme II and equation 1), are alkylated selectively at the α-carbon to the thiocarbonyl group. The unusual β′-lithiation to provide an intermediate $\text{11}$ is observed for N-methyl-α, β-dimetylthioacrylamide and N-methyl-thiocyclohexenecarboxamide.     

Studies on the stability of cycloprop-2-ene carboxylate dianions and reactions with electrophiles

Dianions are generated from alkyllithium reagents and cycloprop-2-ene carboxylic acids, and these dianions can be functionalized by electrophiles at the vinylic position. In a previous report, we described that such dianions could be generated and reacted with electrophiles in Et2O or THF. Upon further study, it was found that there were reproducibility issues for those reactions that were carried out in Et2O. Working under the assumption that an impurity may have promoted these reactions, a detailed study was undertaken to determine the effect of variables on the generation, stability, and reactivity of cycloprop-2-ene carboxylate dianions. It has been found that certain additives can have a substantial effect on the chemistry of cycloprop-2-ene carboxylate dianions. In particular, it was determined that amine N-oxide additives have a beneficial effect both on the stability of cycloprop-2-ene carboxylate dianions and on the rates that such dianions undergo alkylation. Conditions for reacting dianions with a broad range of electrophiles are described.     

Synthesis of quinolines by iron-catalyzed reaction of anilines with propane-1,3-diol

Quinoline and its derivatives were synthesized by cyclocondensation of anilines with propane-1,3-diol in 57–96% yield in the presence of iron-containing catalysts in carbon tetrachloride.     

Preparation of pyrazole and isoxazole libraries on cellulose beads: a new cheap and versatile biopolymer

A cellulose-based resin has been used to prepare a library of pyrazoles and isoxazoles via in situ generation of a polymer-bound enaminone. The synthesis is more versatile and efficient than the methods that had been previously described. Treatment of cellulose-bound enaminone with hydroxylamine or phenylhydrazine afforded the corresponding isomerically pure target heterocycles in high yield directly in solution, restoring the starting cellulose. To cite this article: L. De Luca et al., C. R. Chimie 6 (2003).     

Synthesis of new pyrazole and isoxazole derivatives based on products of condensation of β-dicarbonyl compounds with 1,2,3-trihalopropanes

The reaction of 2-(2-halo-3-propenyl)-1,3-dicarbonyl compounds, which are formed in the alkylation of -dicarbonyl compounds with 1,2,3-trihalopropanes in the presence of potassium carbonate in DMSO, with hydrazine and hydroxylamine derivatives was studied. The synthesis of new pyrazole and isoxazole derivatives on the basis of this reaction is described. Some chemical transformations of the 1,2-azoles obtained were investigated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 787–791, June, 1987.     

A novel reaction of 11,11,12,12-tetracyanoanthraquinodimethane: The formation of 10-dicyanomethylene-anthrone hydrazone

Summary A novel reaction of 11,11,12,12-tetracyanoanthraquinodimethane — its transformation into 10-dicyanomethylene-anthrone hydrazone by reaction with hydrazine — is reported. This hydrazone seems to be a convenient starting material in the synthesis of anthracene derivatives and compounds incorporating anthracenic fragments, but is itself as a conjugated donor acceptor system a material with interesting physical properties.

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Eine neue Reaktion von 11,11,12,12-Tetracyanoanthrachinodimethan: die Bildung von 10-Dicyanomethylen-anthronhydrazon (Kurze Mitt.)

Zusammenfassung Eine neue Reaktion von 11,11,12,12-Tetracyanoanthrachinodimethan — seine Umsetzung zum 10-Dicyanomethylen-anthronhydrazon durch Reaktion mit Hydrazin — wird beschrieben. Dieses Hydrazon könnte als Ausgangsmaterial für die Synthese von Anthracenderivaten dienen, zeigt aber auch selbst als konjugiertes Donor-Akzeptorsystem interessante physikalische Eigenschaften.

     

Synthesis of an enlarged library of dynamic DNA activators with oxime, disulfide and hydrazone bridges

Dynamic amphiphiles have a "bridge" between their charged head and their hydrophobic tails. The presence of dynamic covalent bonds is of interest for differential and biosensing applications as well as for rapid access to the libraries needed to screen for gene delivery or cellular uptake of siRNA. However, efforts to develop libraries have so far concentrated on hydrazone bridges to monocationic heads. Here, we report synthesis efforts to enlarge this focused library with oxime and disulfide bridges and dynamic amphiphiles with more than one positive charge. Evaluation in fluorogenic vesicles reveals best activation of DNA as ion transporters by dynamic amphiphiles with dendritic scaffolds, doubly charged heads and four tails. Moreover, oximes, contrary to hydrazones, remain active under acidic conditions. Linear elongation of dendritic head-groups seems to cause increasing detergent effects and should therefore be avoided.     

Studies on film formation on cathodes using pyrazole derivatives as electrolyte additives in the Li-ion battery

Pyrazole derivatives are flame retardants and provide thermal protection on cathodes, as they help to form a thick protective film. A thicker film provides more protection and delays the thermal decomposition of the cathode. Among the tested pyrazoles, bis(trifluoromethyl)pyrazole (BFTMP) serves as the best flame retardant additive. Additionally, a cell with BFTMP shows better capacity retention than a cell with no additive in full-cell cycle life tests.     

Novel fluorescent probe for the selective detection of organophosphorous nerve agents through a cascade reaction from oxime to nitrile via isoxazole

A novel fluorescent probe based on fluoresceinyloxime was developed for detection of such organophosphorous compounds as nerve agents. The probe underwent an abnormal cascade reaction from oxime to nitrile via isoxazole in aqueous solvent and displayed a highly selective fluorescence response to diethylchlorophosphate (DCP) with the detection limit of 10 nM DCP in HEPES buffer.