Synthesis of pyrazoles via CuI-mediated electrophilic cyclizations of α,β-alkynic hydrazones

Synthesis of pyrazoles via electrophilic cyclization of α,β-alkynic hydrazones by copper(I) iodide is described. When treated with copper(I) iodide in the presence of triethylamine in refluxing acetonitrile, α,β-alkynic hydrazones, prepared readily from hydrazines and propargyl aldehydes and ketones, undergo electrophilic cyclization to afford pyrazole derivatives in good to excellent yields. The reaction appears to be general for a variety of α,β-alkynic hydrazones and tolerates the presence of aliphatic, aromatic, and ferrocenyl moieties with electron-withdrawing and electron-donating substituents.     

Molecular complexes of cyclophanes—XIII. Charge-transfer complexes of cyclophanes with fluoranil

The charge-transfer (CT) complexes of some methylated [2.2]para-, multibridged cyclo- and [2.2]indenophanes as π-donors with fluoranil (TFQ) as π-acceptor have been studied spectrophotometrically. The role of the molecular structure of the donors on their Lewis basicities and stability of their CT complexes with TFQ are discussed. Eight pure crystalline complexes were prepared. Their i.r. spectra indicate an increase of the electron density in the TFQ part of the CT complex.     

Synthesis of β-tosylethylhydrazine and its use in preparation of N-protected pyrazoles and 5-aminopyrazoles

β-Tosylethylhydrazine (6) can be prepared efficiently in one step from commercially available p-tolyl vinyl sulfone (7) and hydrazine hydrate. This hydrazine reacts with both 1,3-diketones and conjugated ynones in glacial acetic acid to provide a variety of N-tosylethyl-protected (TSE) pyrazoles in good yields. The TSE group can be removed from the pyrazoles using potassium t-butoxide in THF at −30 °C-rt. In addition, hydrazine 6 condenses with β-ketonitriles and β-aminoacrylonitriles to afford 5-aminopyrazoles, which can be deprotected by brief treatment with NaOEt in EtOH/DMSO at 45 °C.     

Solution chemistry of lanthanide complexes—III: Spectroscopic studies of lanthanide complexes of glycine and polyglycines

The lanthanide complexes of glycine, diglycine and triglycine have been studied by a variety of physical means. Measurements of differential absorption of Ho(III) complexes, luminescence intensities of Tb(III) complexes, and intermolecular energy transfer from Tb(III) to Eu(III) complexes were all used to characterize the nature of the solution chemistry. The complexes tend to remain mononuclear at low pH, but associate through hydroxide linkages above neutral pH. The degree of association is much less for complexes of diglycine relative to those of glycine, suggesting that the steric nature of the amino acid ligand plays a dominant role in determining the degree of association.     

Vibrational spectra of carboxylato complexes—II. Some oxo-tetranuclear complexes

The i.r. and Raman spectra of the compounds Be₄O(OOCCH₃)₆, Be₄O(OOCCD₃)₆, Be₄O(OOCH)₆ and Zn₄O(OOCCH₃)₆ have been analysed and assigned in detail. In particular, the vibrational modes of the O(MO₃)₄ subunits, and their interactions with the carboxylate ligand vibrations, have been identified. The compound Zn₄O(OOCC₂H₅)₆ has the same oxo-centred structure as the others.     

Fluoro complexes of hexavalent uranium—V: Fluorooxalato complexes of dioxouranium(VI)

The salts of the new types M₂[UO₂F₂(C₂O₄)], M₄[UO₂F₂(C₂O₄)₂] and M₂[(UO₂)₂F₄(C₂O₄)] (where M = potassium and rubidium) have been prepared by mixing saturated solutions of H[UO₂F₃]·H₂O with alkali metal oxalate solutions in cold in different mole ratios. Molecular conductances of the salt solutions indicate that the ions are decomposed in dilute solution to a great extent. The complexes are also completely decomposed on passing their solutions through a column of cation exchange resin in hydrogen form. The IR spectra of the salts of [UO₂F₂(C₂O₄)]²⁻ and [UO₂F₂(C₂O₄)₂]⁴⁻ indicate that oxalate is acting as a normal chelating agent, while the spectra of the salts of [(UO₂)₂F₄(C₂O₄)]²⁻ support that the ion contains bridged oxalate group. The lattice parameters of the three potassium salts have been reported.     

Fluoro complexes of hexavalent uranium—VII: Fluorosulphato complexes of dioxouranium(VI)

The fluorosulphato complexes K₂[U0₂F₂(S0₄)], (NH₄)₂[U0₂(S0₄)], (NH₄)₆[(UO₂)₂F₄(SO₄)₃] and Cs₂[(U0₂)₂F₄(S0₄)] have been prepared by crystallising solutions containing U0₂F₂ and ammonium or the alkali metal sulphates. Another ammonium salt, (NH₄)[U0₂F(S0₄)] has been obtained by the pyrolysis of (NH₄)₂F₂(S0₄)]. Molecular conductance and ion exchange studies show that the complex ions are decomposed in dilute solution. The IR spectra of the complexes indicate that the sulphate ion acts as a bidentate chelating or briged bidentate group C_2v symmetry of sulphate ion The lattice parameters of the potassium and ammonium salts have been reported.     

Infrared intensities of charge transfer complexes—I. Iodine cyanide complexes

Infrared intensities of some ICN complexes were measured in solution, and the observed intensity changes on complex formation were explained on the basis of the electronic reorientation during molecular vibration. Formation constants were obtained as well from i.r. measurements for the purpose of the determination of equilibrium concentrations in the complex solutions.     

Synthesis of BR2 complexes of α-pyrrolyl dipyrrins

A series of BR₂ complexes of α-pyrrolyl dipyrrin were synthesized from BF₂ complex of α-pyrrolyl dipyrrin (3-pyrrolyl BODIPY) by treating it with various alkyl- and aryl magnesium halides under mild Grignard reaction conditions. The BR₂ complexes were functionalized at α-position of the appended pyrrole ring with formyl, chloro and bromo functional groups and these functionalized BR₂ complexes were used further to prepare various novel derivatives of BR₂ complexes. The BR₂ complexes were characterized by HR mass, NMR, absorption, fluorescence, and electrochemical techniques. Two of the BR₂ complexes were structurally characterized by X-ray crystallography. Our studies revealed that the substitution of fluorine atoms at the boron center of 3-pyrrolyl BODIPYs with different alkyl/aryl groups significantly alters their structural, spectral and electrochemical properties. The DFT studies also support the alteration of the electronic properties of the BR₂ complexes.     

Reactions of transition metal σ-acetylide complexes: IX. Preparation and properties of some cycloheptatrienylvinylidene complexes

Addition of [C₇H₇][PF₆] to iron, ruthenium or osmium alkynyl complexes has given eight cationic cycloheptatrienylvinylidene derivatives [M{C C(C₇H₇)R}(L)₂ (η-C₅H₅)][PF₆] (M = Fe, Ru or Os; R = Me, Pr, Ph or C₆F₅; L = PPh₃, L₂ = dppm or dppe; but not all combinations). With Fe(C₂Ph)(CO)₂(η-C₅H₅), only [Fe(CO)₂(thf)(η-C₅H₅)][PF₆] was obtained. Reactions of the new complexes are characterised by loss of the C₇H₇ group. The NMR spectra and FAB mass spectra are described in detail.     

Charge-transfer complexes of benzanilides with π-acceptors

Spectrophotometric studies of several substituted benzanilides as electron donors with tetracyanoethylene (TCNE) and 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) as electron acceptors have given results that are consistent with an interpretation of 1:1 charge-transfer (CT) complexes. The nature of interaction as well as the substituent effects on the CT complexation are discussed.     

Iron-catalyzed aminolysis of β-carbonyl 1,3-dithianes: synthesis of stereodefined β-enaminones and 3,4-disubstituted pyrazoles

A novel iron-catalyzed aminolysis of β-carbonyl 1,3-dithianes with various amines including ammonia, primary and secondary amines, as well as hydrazine hydrate has been developed, leading to the synthesis of stereodefined β-enaminones and 3,4-disubstituted pyrazoles in good to high yields.     

Solubility characteristics ofβ-cyclodextrin inclusion complexes

Some inclusion complexes of-cyclodextrin (cyclomaltoheptaose) have been investigated, particularly with respect to their solubility. The mathematical characterization of the equilibrated host-guest system containing both solid and solution phases is discussed (first of all those, which contain 1:1 or 1:1 + 2:1 species) and demonstrated by different examples.     

Vibrational spectra of carboxylato complexes—IV. Mixed-metal and mixed-valence oxo-trinuclear complexes

Infrared spectra of mixed-metal complexes [Cr_3-nFe_nO(OOCR)₆L]⁺ (n = 1,2; R = H, CH₃; L = H₂O, γ-picoline, pyridine), and of mixed-valence complexes [Fe^III₂Fe^IIO(OOCCH₃)₆py₃], [Ru^III₂Ru^IIO(OOCCH₃)₆L₃] (L = H₂O, P(C₆H₅)₃) are reported and compared with analogous symmetrical (Cr^III)₃, (Fe^III)₃ and (Ru^III)₃ species. The effects of lowered symmetry are seen in the mixed-metal but not in the mixed-valence complexes.     

Facile one-pot synthesis of 5-substituted isoxazoles and pyrazoles through microwave-promoted intramolecular cyclization of γ-hydroxyalkynal oximes and hydrazones

Simple and efficient one-pot synthesis of 5-substituted isoxazoles and pyrazoles has been developed. The formation of the target isoxazoles and pyrazoles is initiated by 1,2-nucleophilic addition of generated in situ hydroxylamine or hydrazine to α-acetylenic γ-hydroxyaldehydes with further intramolecular cyclization of the adducts. The protocols are associated with readily available substrates, simple procedure, short reaction time, and moderate to high yields.     

Inclusion complexes of alcohols with α-cyclodextrin

Calorimetric studies of the inclusion complexes of straight and branched alcohols and of diols with alpha-cyclodextrin (-CD) have been carried out in water solvent. The data suggest that straight and branched chain alcohols enter the cavity of -CD alkyl end first. The hydroxyl group hydrogen bonds to the outer oxygen ring of the cyclodextrin. For branched chain alcohols the longer alkyl part of the molecule penetrates the -CD cavity up to the hydroxyl group. Diols form two hydrogen bonds to the outer oxygen ring of the cyclodextrin with some penetration into its interior.     

Metal complexes as ligands—VII: The chemistry of the monothiooxalate complexes

A synthesis of potassium monothiooxalate, K₂C₂SO₃, and its reactions with metal ions are reported. The spectroscopic properties of the complexes, M(C₂SO₃)_nⁿ⁻, for M  Ni(II), Cu(II), Zn(II) (n = 2); and M  Cr(III), Co(III), Fe(III) (n = 3) are indicative of (SO) chelated ligands while the Al(III) (n = 3) complex is an (OO) bonded chelate. The copper(II) complex undergoes an irreversible oxidation at 0.43 V. This oxidation is accompanied by reduction of the copper(II) and evolution of CO₂ and SCO.The inert cations which accompany the anionic monothiooxalate complexes are readily replaced by the coordinatively unsaturated (Ph₃P)₂M⁺, M  Ag(I), Cu(I) complex cations. The bridging of the monothiooxalate ligand in the resulting polynuclear complexes is of the type MOOC₂SOM′, M  Al(III), Fe(III), M′  Ag(I), Cu(I); M  Cr(III), M′  Cu(I) and MSOC₂O₂M′, M  Cr(III), Co(III), M′  Cu(I).     

Comprehensive studies of Tolperisone·HCl-cyclodextrin complexes

Solid inclusion complexes of TolperisoneHCl with five various cyclodextrins were prepared by kneading and spray drying. The complex formation between the drug and the cyclodextrins were proven using thermoanalytical methods, X-ray diffraction, IR spectroscopy. The results of the solid state investigations were supported by the liquid phase investigations, such solubility and parition constant measurements and stability constant determination. Among all cyclodextrins used the - and -CD-s were found to be the best complexing agents.     

Inclusion complexes of β-cyclodextrin with dihydroxyphenols of various nature

The ways for the practical preparation of stable inclusion complexes of β-cyclodextrin with dihydroxyphenols of various nature are developed. Mutual orientation of hydroxy groups and the nature of the bridge in the bisphenols are shown to affect considerably their ability to the complex formation.