Volatile iridium(I) complexes with β-diketones and cyclooctadiene: syntheses,structures and thermal properties

A series of volatile mixed-ligand iridium(I) complexes [Ir(cod)(L)] (cod = cyclooctadiene-1,5, L = R¹C(O)CHC(O)R², R¹ = CF₃, R² = CF₃ – hfac 1, Me – tfac 2; ^tBu – ptac 3, Ph – btfac 4, R¹ = R² = Me – acac 5; ^tBu – thd 6) was synthesized and investigated in terms of usage in metal-organic chemical vapor deposition processes. Compounds 3 and 4 were obtained for the first time. All compounds were investigated by elemental analysis, NMR spectroscopy, thermogravimetry, and mass spectrometry. Crystal structures of 2–4 and 6 were determined by single-crystal XRD. The influence of β-diketonate ligand on the thermal properties of complexes in condensed and gas phase was revealed. The following volatility order was arranged: L = hfac 1 > tfac 2 ≈ ptac 3 > acac 5 > thd 6 > btfac 4. Complexes 1 and 6 vapors demonstrated the lowest and the highest thermostability, respectively.     

Interaction of fluoroalkyl-containing β-diketones with amines

The composition of products of the interaction of asymmetric fluoroalkyl-containing -diketones with amines was studied. Mixtures of regioisomeric -aminovinylketones and products of cleavage and secondary condensation are formed, depending on the temperature, the solvent, the nature of the fluorinated and nonfluorinated substituents in the -diketone, and the basicity of the amine. The major product is a -aminovinylketone in which the NH₂ group is removed from the fluoroalkyl substituent. No -aminovinylimines, products of condensation involving two electrophilic centers, were observed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2278–2284, September, 1996.     

Solvent-dependent supramolecular assemblies of π-conjugated anion-responsive acyclic oligopyrroles

Amide-attached pyrrole-based π-conjugated anion receptors showed solvent-dependent assembled modes such as H-aggregates that were soluble in octane and highly organized structures that provided supramolecular gels in CH(2)Cl(2) and 1,4-dioxane in the absence of π-π stacking.     

Synthesis and luminescence-spectral properties of benzoheterocyclic β-diketones and their complexes with europium

In order to solve some environmental and biomedical problems, we synthesized fluorinated heterocyclic β-diketones and estimated the luminescence-spectral properties of these compounds complexes with the ions of rare-earth elements as the possible reagents for immunofluorescence analysis.     

Electronic state and photosensitivity of metal alkoxides chemically modified with β-diketones

Electronic state and optical absorption spectra of metal alkoxides stabilized with β-diketones (with a variety of substituents) were calculated using first-principle molecular orbital methods. The characteristics of the optical absorption and the mechanism of the photodissociation of alkoxides with irradiation of light are discussed. The position of the first peak observed in the near UV region in the theoretical spectra corresponded to that observed in the experimental spectra with a 25 nm shift toward shorter wavelengths. The first absorption peak observed in the visible range originated from electronic transitions to molecular orbitals, including the antibonding components of the C–O bonding in the chelate ring. The results suggested that the bonding of the chelate rings should be important in controlling the photosensitivity of chemically modified titanium alkoxides.     

Heteroleptic europium complexes with β-diketones and trifluoroacetic acid

Europium complexes with β-diketones and trifluoroacetic acid were obtained and characterized using elemental analysis, IR spectroscopy, emission spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetry. The europium complexes are more stable when fluorinated substituents in β-diketones are replaced by alkyl substituents. Both the ligands (β-diketone and trifluoroacetic acid) are coordinated in a bidentate fashion. The Stark splitting of the ⁷ F ₁ levels in the complexes obtained increases with an increase in the negative inductive effect of the substituents in β-diketones, which indicates the partially ionic character of the Eu-ligand bond.     

SmI2-mediated cross-coupling of nitrones with β-silyl acrylates: synthesis of (+)-australine

The SmI(2)-mediated cross-coupling of nitrones with β-silyl-α,β-unsaturated esters, followed by zinc reduction, allows an efficient and highly diastereoselective preparation of β-silyl lactams, which are precursors of β-hydroxy lactams through Tamao-Fleming oxidation. By applying the method to a cyclic, carbohydrate-derived nitrone, a new synthesis of (+)-australine has been realized in only 11 steps and in 21% overall yield from L-xylose.     

SmI2-mediated coupling of nitrones and tert-butanesulfinyl imines with allenoates: synthesis of β-methylenyl-γ-lactams and tetramic acids

Nitrones and tert-butanesulfinyl imines undergo conjugate addition to alkyl allenoates under SmI(2)-mediated reductive coupling conditions to produce novel β-methylenyl-substituted γ-amino esters. The latter were readily transformed into the corresponding β-methylenyl-γ-lactams by simple zinc reduction (N-hydroxy amines) or by acid hydrolysis (sulfinamides). The diastereoselective preparation of various β-methylenyl-γ-lactams offers a route to tetramic acids, the key structural features of an important class of bioactive natural products.     

α-Tosyloxylation of fluorosubstituted β-diketones

The interaction of fluorinated -diketones with [hydroxy(tosyloxy)iodo]benzene leads to -tosyloxy--diketones existing in the form of stable hydrates.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 541–542, March, 1994.     

Heterocyclization of michael adducts of β-diketones with arylmethylidene derivatives of malononitrile dimers

Reaction of arylmethylidene derivatives of malononitrile dimer with 1,3-cyclohexanediones in anhydrous methanol in the presence of sodium methylate as catalyst affords 4-amino-5-aryl-2-methoxy-6-oxo-5,6,7,8,9,10-hexahydrobenzo[b][1,8]naphthyridine-3-carbonitrile. In the presence of strong electron-donor substituents in the benzene ring the reaction takes another route resulting in 4-amino-2-aryl-6-methoxypyridine-3,5-dicarbonitriles.     

The structure and EPR spectra of binuclear copper(II) complexes with acyldihydrazones of β-diketones

The synthesis and structure of binuclear copper(II) complexes with acyldihydrazones of some β-diketones are described. The molecular structure of the copper(II) complex [Cu₂L·4Py] with trifluoroacetylacetone succinyldihydrazone (H₄L) was determined by the single-crystal X-ray analysis. Central atoms are bridged by a chain of seven σ-bonds with a Cu...Cu distance of 8.750 Å. EPR spectra of copper(II) complexes with acyldihydrazones of trifluoroacetylacetone and lower dicarboxylic acids containing from one to four methylene groups in the aliphatic spacer show the seven-line HFS due to spin-spin coupling of unpaired electrons with the two equivalent copper nuclei (g = 2.110, a = (38.5–40.5)⊙10^?4 cm^?1). By extending polymethylene spacer, as well as by modifying starting β-diketone, an exchange interaction between paramagnetic centers is suppressed.     

Original syntheses of carbonyl compounds and gem-dihalocyclopropanes from β-hydroxyalkylselenides

β-hydroxyalkylselenides possessing two alkyl substituents on the carbon bearing the selenenyl moiety react with dihalocarbenes generated from haloforms and thallous ethoxide or under phase transfer catalysis to produce ring enlarged ketones as the sole product in the first case, as the main product in the second. The reaction takes another course when the dihalocarbenes generated from haloforms and tBuOK or from trihalomethylphenylmercury are employed and leads inter alias to dihalocyclopropanes.     

Catalyst-free direct synthesis of β-enaminones through reaction of benzohydrazonamides with cyclic 1,3-diketones: Access to exocyclic β-enaminones

Abstract

The reaction of benzohydrazonamides with cyclic 1,3-diketones affords β-enaminones in good to excellent yields (14 examples, 69???89%). This transformation proceeds under mild reaction conditions (ethyl acetate, 25?°C, 12???24?h) in the absence of any catalyst and gives access to novel nitrogen-rich organic scaffolds.     

Convenient syntheses of cyclic carbonates by new reaction of oxiranes with β-butyrolactone

Cyclic carbonates were synthesized by reactions of the corresponding oxiranes with β-butyrolactone using quaternary salts such as tetrabutylammonium bromide or 18-crown-6 = KBr as a catalyst.     

A facile synthesis of trisubstituted alkenes from β-diketones and aldehydes with AlCl3 as catalyst

Preparation of trisubstituted alkenes from low-activity β-diketones and aldehydes with aluminum chloride as catalyst has been studied. The frequently used catalyst AlCl₃ is used for the first time to promote this condensation. The procedure is a convenient, low toxicity, and highly efficient method for industrial synthesis of trisubstituted alkenes in high yield.     

Crystal structures of hafnium(IV) and zirconium(IV) complexes with β-diketones

Preparation methods are developed for a number of 7- and 8-coordinated derivatives of Hf(IV) and Zr(IV) with β-diketonate ligands (R¹-CO-CH-CO-R²). The complexes obtained are examined by IR spectroscopy, mass spectrometry, and X-ray crystallography. All structures are molecular. The M-O distances fall within 2.09–2.28 Å. In the crystals, the molecules are joined only by van der Waals interactions. It is demonstrated that the series of hafnium(IV) and zirconium(IV) chelates with identical ligands are isostructural, and the introduction of CF₃- or tert-butyl groups in the terminal positions of the ligand as well as chlorine substitution for one of the ligands do not essentially affect the basic geometric characteristics of the ligand in the complexes.     

Synthesis of CF3-containing β-hetaryl-substituted enones

A procedure was developed for the synthesis of previously unknown CF₃-containing -azolyl-substituted enones by the reactions of 1,1,1-trifluoro-4-sulfonyl-3-butene-2,2-diols with various azoles. Quaternization of the azolyl group with methyl triflate afforded -azolium-substituted enones in quantitative yields.