Molecular and Electronic Structure of Trimethylsilylpropiolamides

The specific features of molecular and electronic structure of trimethylsilylpropiolic acid amides were studied by means of IR spectroscopy and quantum chemistry (AM1). The competition between p,-conjugation in the amide fragment and ,-conjugation in the ethynylcarbonyl group CC-C=O was established. The prevailing conformers were revealed, their geometrical parameters were established, the barriers to internal rotation around the amide C-N bond were calculated for acyclic (13 kcal mol^-1) and heterocyclic (8.12 kcal mol^-1) amides.     

Spectroscopic investigation of ground state pyrrole (C4H5N): the NH stretch

We have recorded the infrared absorption spectrum of pyrrole at 0.005 cm⁻¹ spectral resolution using a Fourier transform interferometer. The rotational analysis of the fundamental N---H stretch (1¹₀) at 3530.811343(82) cm⁻¹ was performed. A set of 13 upper state rovibrational parameters was determined, allowing the 2715 assigned rovibrational lines to be reproduced with a standard deviation of 1.3 10⁻³ cm⁻¹. An attempt to record the fundamental band under slit-jet conditions is reported. The role of hot bands accompanying the series of the N---H stretch excitation is investigated. Effective vibrational parameters — ω⁰₁, X⁰₁₁, Y₁₁₁, X_1,24 — are obtained. The lower level in the hot band series is unambiguously identified as the V₂₄ = 1 level, by retrieving X_1,24 independently, from other spectral data. The observation of the complex band pattern accompanying the N---H series in the higher overtone range is discussed with the help of new data, recorded around the 1⁵₀ band at different temperatures using intracavity laser optoacoustic spectroscopy.     

Reactions of 4,7‐dihydro‐1,2,4‐triazolo[1,5‐a]pyrimidines with α,β‐unsaturated carbonyl compounds

The reaction of 5,7‐diphenyl‐4,7‐dihydro‐1,2,4‐triazolo[1,5‐a]pyrimidine ( 1 ) with α,β‐unsaturated carbonyl compounds 2a‐f led to the formation of the alkylated heterocycles 3a‐f (Figure 1). However, the reaction of 5‐methyl‐7‐phenyl‐4,7‐dihydro‐1,2,4‐triazolo[1,5‐a]pyrimidine ( 5 ) with 2a‐c yielded under the same conditions the triazolo[5,1‐b]quinazolines 6a‐c (Figure 3). In this case, the alkylation is followed by a cyclocondensation. The structure elucidation of the products is based on ir, ms, ¹H and ¹³C nmr measurements and on an X‐ray diffraction study.     

Analysis of conjugated linoleic acids as 9-anthrylmethyl esters by reversed-phase high-performance liquid chromatography with fluorescence detection

A simple and highly sensitive method for determining the fatty acid composition of food lipids containing conjugated linoleic acid (CLA) is described. The method is based on the separation of the 9-anthrylmethyl ester derivatives of saturated and unsaturated (conjugated and non-conjugated) fatty acids by reversed-phase high-performance liquid chromatography with fluorescence detection. Just like the other fatty acids, CLA reacts readily with 9-anthryldiazomethane at room temperature to produce 9-anthrylmethyl esters without isomerization and decomposition of the conjugated double bonds. Clear resolution of the individual fatty acids as their 9-anthrylmethyl esters is achieved on a highly efficient octadecylsilylated silica column (150- x 3-mm i.d., 3-microm particle size) using a stepwise gradient elution with methanol-water. The method is standardized with commercially available CLA isomers (cis-9, trans-11 and trans-10, cis-12-octadecadienoic acids, and their cis,cis and trans,trans isomers) and applied for determination of the fatty acid compositions of milk and sdairy products.     

O-acylated flavonoid glycosides from the needles ofPicea obovata II. 3′- and 6′-isomers of p-coumaroylastragalin

Two monoacylated glycosides have been isolated from the needles ofPicea obovata — the previously unknown 3-p-coumaroylastragalin (I) and 6-p-coumaroylastragalin (II). It has been established that under the conditions of mild saponification and acid hydrolysis isomerization of (I) into (II) and the splitting out of the acy1 residue takes place. The position of the acy1 substituent has been shown by PMR spectroscopy using the INDOR method. The physicochemical characteristics of the acylated glycosides and of their heptaacetates are given.All-Union Scientific-Research Institute of Medicinal Plants, Moscow. Irkutsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR, Moscow. I. M. Sechenov First Moscow Medical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 186–190, March–April, 1980.     

Redox reactions of arabinogalactan with silver ions and formation of nanocomposites

Formation of silver nanoparticles in the course of chemical reduction of AgNO₃ with arabinogalactan in aqueous alkaline solution was studied by electronic absorption spectroscopy and X-ray diffraction analysis. The pH of the solution was found to be the major factor affecting the degree of reduction of Ag⁺ ions. The probable reaction mechanism was discussed. Composites containing up to 58% Ag, with the metal particle size of 7–16 nm, were prepared. The nanoparticle size can be controlled by varying the reactant ratio AgNO₃: arabinogalactan. Chemical modification of arabinogalactan was confirmed by IR and ¹³C NMR spectroscopy and by TLC.     

Nitrile-amidine coupling at Pt(IV) and Pt(II) centers. An easy entry to imidoylamidine complexes

Treatment of trans-[PtCl4(RCN)2] (R = Me, Et, Ph, NEt2) with 2 equiv of the amidine PhC(=NH)NHPh in a suspension of MeCN (R = Me), CHCl3 (R = Et, Ph), or in CHCl3 solution (R = NEt2) results in the formation of the imidoylamidine complexes trans-[PtCl4{NH=C(R)N=C(Ph)NHPh}2] (1-4) isolated in good yields (66-84%). The reaction of soluble complexes 3 and 4 with 2 equiv of Ph3P=CHCO2Me in CH2Cl2 (40 degrees C, 5 h) leads to dehydrochlorination resulting in a chelate ring closure to furnish the platinum(IV) chelates [PtCl2{NH=C(R)NC(Ph)=NPh}2] (R = Ph, 5; R = NEt2, 6), accordingly, and the phosphonium salt [Ph3PCH2CO2Me]Cl. Treatment of 5 with 3 equiv of Ph3P=CHCO2Me at 50 degrees C for 5 d resulted in only a 30% conversion to the corresponding Pt(II) complex [Pt{NH=C(NEt2)NC(Ph)=NPh}2] (15). The reduction can be achieved within several minutes, when Ph2PCH2CH2PPh2 in CDCl3 is used. When the platinum(II) complex trans-[PtCl2(RCN)2] is reacted with 2 equiv of the amidine, the imidoylamidinato complexes [PtCl(RCN){NH=C(R)NC(Ph)=NHPh}] (8-11) and [PhC(=NH)NHPh] x HCl (7) are formed. The reaction of trans-[PtCl2(RCN)2] with 4 equiv of the amidine under a prolonged reaction time or treatment of [PtCl(RCN){NH=C(R)NC(Ph)=NHPh}] (8-11) with 2 more equiv of the amidine yields the complex bearing two chelate rings [Pt{NH=C(R)NC(Ph)=NHPh}2] (12-15). The treatment of cis-[PtCl2(RCN)2] (R = Me, Et) with the amidine gives ca. 50-60% yield of [PtCl2{NH=C(R)NHC(Ph)=NHPh}] (16 and 17). All of the platinum compounds were characterized by elemental analyses; FAB mass spectrometry; IR spectroscopy; 1H, 13C{1H}, and 195Pt NMR spectroscopies, and four of them (4, 6, 8, and 15) were also characterized by X-ray crystallography. The coupling of the Pt-bound nitriles and the amidine is metal-mediated insofar as RCN and PhC(=NH)NHPh do not react in the absence of the metal centers in conditions more drastic than those of the observed reactions. The nitrile-amidine coupling reported in this work constitutes a route to the synthesis of imidoylamidine complexes, some of them exhibiting luminescent properties.     

Intramolecular Dynamics and Molecular Structure of Europium(III) Chelate Complexes with Crown Ethers as Studied by NMR Spectroscopy

Earlier the intramolecular inversion of the 18-crown-6 molecules was found in the complex ion pairs [Ln(ptfa)₂ (18-crown-6)]⁺ [Ln(ptfa)₄]⁻ (H₂O)₄ where Ln = La(1), Ce (2), Pr (3), Nd (4), and ptfa is 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione. In this work the peculiarities of the molecular structure and dynamics were studied for [Eu(ptfa)₂ (18-crown-6)]⁺ [Eu(ptfa)₄]⁻ (H₂O)₄ (5) by NMR spectroscopy techniques. Through VT-NMR spectra analysis the temperature dependence was obtained for the rate constant. The free energy ΔG^‡(320) of 18-crown-6 ring inversion activation was found to be 65 ± 5 kJ mol⁻¹ for 5 in CDCl₃. This result is comparable with the earlier data [S.P. Babailov and D.A. Mainichev: J. Inclusion Phenom. Macrocyclic Chem. 43, 187–193 (2002)] for complexes 2, 3, 4 in deuterated toluene (ΔG^‡(320)=65 ± 9, 64 ± 9, 64 ± 9 kJ mol⁻¹ respectively). It was found by relaxation NMR spectroscopy that the effective distance between Ln and protons of the crown molecule is 4.5 ± 0.2 Å. The analysis of structural parameters testifies that the crown ether and chelated anions are in the first coordination sphere of a Ln cation. Obtained geometrical parameters show that the complex cations of Eu, Ce and Pr have similar spatial structures.This revised version was published online in July 2005 with a corrected issue number.     

Heterocyclic nitro compounds

Ketones of the 3-nitro-5-R-1,2,4-triazole series react with hydrazoic acid in concentrated sulfuric acid to give triazolyl-substituted acetamides. Acid hydrolysis of the latter leads to 1-aminoalkyl-3-nitro-5-R-1,2,4-triazoles. Intramolecular cyclization with the elimination of HNO₂ and the formation of 2-nitro-5,6-dihydro-1H-imidazo[2,3-b]-1,2,4-triazole was noted in the case of 1-(2-aminoethyl)-3,5-dinitro-1,2,4-triazole.See [1] for communication XX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1271–1273, September, 1977.     

Complexing processes in M(II)-dithiomalonamide-diacetyl triple systems (M= Ni,Cu) in ethanol solution and in a metal(II)hexacyanoferrate(II) gelatin-immobilized matrix materials

The complexing processes in the M ^II -dithiomalonamide-diacetyl triple system (M=Ni, Cu) occuring in the nickel(II)- and copper(II)hexacyanoferrate(II) gelatin-immobilized matrix in contact with aqueous alkaline solutions (pH~12) containing dithiomalonamide and diacetyl at room temperature, and between MCl₂, dithiomalonamide and diacetyl in EtOH solutions upon heating to$80°C, have been studied. In the Ni ^II -dithiomalonamide-diacetyl system, template synthesis occurs in EtOH solution but does not occur in the gelatin-immobilized matrix, whereas in the Cu ^II -dithiomalonamide-diacetyl system, template synthesis occurs in the gelatin-immobilized matrix but not in EtOH solution. Dithiomalonamide and diacetyl are the ligand synthons in the processes indicated.