Photoisomerization kinetics of trifloxystrobin

The photoisomerization kinetics of trifloxystrobin (TFS) in acetone under artificial sunlight is reported. HPLC analysis showed the TFS, a strobilurine fungicide of EE conformation, was converted into an equilibrium mixture of four isomers after illumination for 7 h. The isomers were identified as EZ, EE, ZZ, and ZE and were separated in the crystalline form by preparative HPLC and characterized by use of a variety of spectroscopic techniques. The quantum yield and reaction constants for the isomerization reactions were determined. The detailed spectral features of the individual isomers measured by UV, IR, Raman, NMR and mass spectroscopy are presented and compared. The spectra of the isomers were found to be very characteristic, with good analytical significance.     

Diastereomeric isomerization of hetaryl leuco-TAM dyes, (2Z, 2′E)-2,2′-(2-phenyl propane-1,3-diylidene)bis(1,3,3-trimethylindoline) derivatives in various organic solvents

The diastereomeric isomerization of the ZE isomers of (2Z, 2′E)-2,2′-(2-phenyl propane-1,3-diylidene) bis(1,3,3-trimethylindoline) derivatives were examined by ¹H NMR spectroscopy in various organic solvents. In non-polar solvents, such as benzene, THF, and chloroform, the ZE isomers of these molecules equilibrated into a mixture of ZE/EE or ZE/EE/ZZ isomers with time, whereas the isomers were inert in polar organic solvents, such as acetone and DMSO. Theoretical calculations of the energies and dipole moments of the diastereomers in different media were performed using the Jaguar program.     

Assignment of the E,Z configurational isomers of platinum complexes of N,N‐dialkyl‐N′‐acyl(aroyl)thioureas by means of triple resonance 1H/13C/195Pt PFG correlation NMR spectroscopy

Unsymmetrical, dialkyl‐substituted N,N‐dialkyl‐N^′‐acyl(aroyl)thioureas show E,Z configurational isomerism at room temperature in solution, which is also expressed in the existence of cis‐[Pt(ZZ‐L‐S,O)₂], cis‐[Pt(EZ‐L‐S,O)₂] and cis‐[Pt(EE‐L‐S,O)₂] complexes derived from these ligands. These configurational isomers were assigned by means of a double magnetization transfer ¹H/¹³C/¹⁹⁵Pt correlation NMR experiment, despite the fact that the long‐range ⁵J(¹⁹⁵Pt, ¹H) and ⁴J(¹⁹⁵Pt, ¹³C) scalar couplings are not directly observable in their ¹H and ¹³C spectra at high field. Depending on the ligand structure, the relative amounts of cis‐[Pt(ZZ‐L‐S,O)₂], cis‐[Pt(EZ‐L‐S,O)₂] and cis‐[Pt(EE‐L‐S,O)₂] complexes are in the ranges 40–42% ZZ, 46–47% ZE and 12–13% EE. The cis‐bis[N‐methyl‐N‐(tert‐butyl)‐N^′‐(2,2‐dimethylpropanoyl)thioureato]platinum(II) complex is found to occur exclusively as the ZZ isomer. Copyright © 2003 John Wiley & Sons, Ltd.     

(EZ)-Cyclobilirubin formation from bilirubin in complex with serum albumin derived from various species

We determined the specificity of photochemical changes of bilirubin in complex with serum albumin from various species. There were no general trends in the configurational photoisomerizations of (ZE)-bilirubin/(ZZ)-bilirubin and (EZ)-bilirubin/(ZZ)-bilirubin associated with the albumins from various species as compared to those associated with human serum albumin. The absorbance spectra of bilirubin in complex with albumins from various species differed, indicating that the three-dimensional structures of (ZZ)-bilirubin bound to the various serum albumins, which are substrates of (ZE)- and (EZ)-bilirubin, differ among species. The rates of conversion of the (EZ)-bilirubin isomer into the structural cyclobilirubin isomer were similar for the albumins of chicken, rat, rabbit, dog, bovine, and pig, and were significantly slower than the rate for human serum albumin. This suggests that the three-domain human albumin has evolved to allow ready conversion of (EZ)-bilirubin to (EZ)-cyclobilirubin. Cyclobilirubin formation in a bilirubin-alpha-fetoprotein solution was much lower than that in a bilirubin–human serum albumin solution. It is believed that the ability of human serum albumin to facilitate the photochemical change of bilirubin was evolutionarily selected in response to neonatal jaundice in humans.     

Study of spontaneous E/Z isomerization of bis[(Z)‐cyanomethylidene]‐diazapentacyclodienedicarboxylates by 1H, 13C,and 15N NMR spectroscopy,X‐ray,and quantum chemical calculation data

X‐ray data show that the diethyl 6,13‐bis[(Z)‐cyanomethylidene]‐5,5,14,14‐tetramethyl‐4,15‐dioxa‐7,12‐diazapentacyclo[9.5.2.0^2,10.0^3,7.0^12,16]octadeca‐8,17‐diene‐10,17‐dicarboxylate is formed as the ZZ isomer and diastereomer with the (1R*,2R*,3R*,10S*,11R*,12R*,16R*) configuration. The ¹H, ¹³C, and ¹⁵N NMR data exhibit that on standing in chloroform‐d solution, there is a spontaneous isomerization of this compound resulting in a thermodynamically stable mixture of the ZZ, ZE, EE, and EZ isomers with the same backbone. Using the 2D [¹H–¹H] COSY, [¹H–¹³C] HSQC, and [¹H–¹³C, ¹H–¹⁵N] HMBC NMR techniques and quantum chemical calculations makes it possible a complete assignment of signals in the ¹H, ¹³C, and ¹⁵N NMR spectra of each of the isomers. Such isomerization does not occur for similar compounds with the more bulky substituents at the 1,3‐oxazolidine rings. Copyright © 2016 John Wiley & Sons, Ltd.     

Novel stilbene‐based Fischer base analog of leuco‐TAM – (2E,2′Z)‐{2‐(4‐(E)‐styrylphenyl)propane‐1,3‐diylidene}bis(1,3,3‐trimethylindoline) – derivatives: synthesis and structural consideration by 1D NMR and 2D NMR spectroscopy

We report the synthesis of a series of novel stilbene‐based (St) Fischer base analogs of leuco‐triarylmethane (LTAM) dyes by treating Fischer base with (E)‐4‐styrylbenzaldehyde derivatives. All St‐LTAM molecules examined herein are characterized by 1D and 2D NMR. They were found to exhibit ZE configuration and isomerize to their diastereomers EE and ZZ in 2–3 h. They exhibit type I behavior of diastereomeric isomerization. Copyright © 2015 John Wiley & Sons, Ltd.     

Identification by GC—MS of cymene isomers and 3,7,7-trimethylcyclohepta-1,3,5-triene in essential oils

Retention indices of cymene isomers published in popular GC—MS atlases were found to be erroneous by analyzing synthetic samples. The following retention indices (RI) were found using a nonpolar phase (diphenyl: dimethylpolysiloxane, 5:95) for four essential-oil components with indistinguishable mass spectra: 3,7,7-trimethylcyclohepta-1,3,5-triene (RI = 970), m-cymene (RI = 1022), p-cymene (RI = 1024), and o-cymene (RI = 1039). The relative distributions of these compounds were evaluated based on the analysis of about 1000 essential oils. Simple methods were given for preparing standard mixtures of isomeric compounds for identification by GC—MS. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 569–571, November–December, 2006.     

Konfigurations- und konformationsisomere antiaromatische [28]Tetraoxaporphyrinoide(4.2.4.2) und aromatische [26]Tetraoxaporphyrin(4.2.4.2)-dikationen. Eine neue Form molekularer Dynamik in makrocyclischen Systemen

Configurational and Conformational Isomeric Antiaromatic [28]Tetraoxaporphyrinoids(4.2.4.2) and Aromatic [26]Tetraoxaporphyrin(4.2.4.2) Dications. A New Type of Molecular Dynamics in Macrocyclic Systems The [28]tetraoxaporphyrinoids(4.2.4.2) 6 are synthesized by cyclizing Wittig reaction of (E, E)-5, 5′-(buta-1, 3-diene-1, 4-diyl)bis[furan-2-carbaldehyde] (8) with (E, E)-{(buta-1, 3-diene-diyl)bis[(furan-5, 2-diyl)methylene]}bis-[triphenylphosphonium] dibromide (9) and 3, 3′-{[(E)-ethene-1, 2-diyl]bis(furan-5, 2-diyl)}bis[(E)-prop-2-enal] ( 22 ) with (E)-{(ethene-1, 2-diyl)bis[(furan-5.2- diy)methylene]}bis[triphenylphosphonium] dibromide ( 23 ). An alternative path to get 6 is the McMurry condensation of 8 . Four different configurational isomers of 6 could be isolated and characterized by ¹H-NMR spectroscopy. The (Z, EE, Z, EE)-isomer 6a is the first macrocyclic system where the inner and outer protons of the (E, E)-dienediyl bridges exchange by rotation around the adjacent single bonds. In the (Z, EE, E, EE)-isomer 6b , the (E)-ethenediyl bridge is rotationally active, while in the (E, ZE, E, EZ)-isomer 6c and in the (E, EZ, E, EZ)-isomer 6e , the rotation of both (E)-ethenediyl bridges is observed. When in the dynamic systems the rotation of the active (E)-double bonds at temperatures T < ?90° is frozen, all configurational isomers of 6 appear to be antiaromatic and paratropic. The oxidation of the [28]tetraoxaporphyrinoids 6c and 6e with DDQ yields the aromatic, diatropic [26]tetraoxaporphyrin(4.2.4.2) dications 21e/21e ′ both with (E, EZ, E, EZ)-configuration but different fixed conformations. (Z, EE, Z, EE)-Isomer 6a is oxidized to give the (Z, EE, Z, EE)-dication 21a , while the oxidation of 6b yields a mixture of 21a and 21e/21e ′. The standard formation enthalpies of the obtained and expected [28]tetraoxaporphyrinoids 6 and [26]tetraoxaporphyrin dications 21 have been calculated with the AM1 method, showing good accordance with the experimental results.     

A theoretical study of keto-enol isomerism and internal rotation in the H<Subscript>2</Subscript>Salen molecule,N,N′-ethylene-bis(salicylidenimine) — schiff base

Geometric parameters, vibrational spectra, and the energies of isomerization of seven keto-enol isomeric forms of the H₂Salen molecule (N,N′-ethylene-bis(salicylidenimine)) are calculated using electron density functional theory (DFT/B3LYP) and correlation consistent valence triple-zeta Gaussian basis sets (cc-pvtz). The isomer with two enol groups (EE₁) and C ₂ symmetry configuration is most energetically favorable. Calculations of the keto-enol equilibrium show that at T ≥ 250 K the H₂Salen gas phase is a mixture of four conformers (rotamers of the main isomer EE₁). The contribution of other isomers does not exceed a few percent. The NBO analysis reveals that the system of π-conjugated bonds involves not only the atoms of the benzene moiety, but also the O, C, and N atoms nearest to the benzene ring. The energy stabilization of the isomer EE₁ is shown to be due to the presence of two strong intramolecular N...H hydrogen bonds. Intramolecular N...H and O...H hydrogen bonds are observed in all other isomers. The bathochromic shift of O-H and N-H vibrational frequencies, caused by the effect of hydrogen bonds, is 520–790 cm⁻¹.     

Determination of arsenic species and arsenosugars in marine samples by HPLC–ICP–MS

Arsenic-speciation analysis in marine samples was performed by high-pressure liquid chromatography (HPLC) with ICP–MS detection. Separation of eight arsenic species—As^III, MMA, DMA, As^V, AB, TMAO, AC and TeMAs⁺—was achieved on a C₁₈ column with isocratic elution (pH 3.0), under which conditions As^III and MMA co-eluted. The entire separation was accomplished in 15 min. The HPLC–ICP–MS detection limits for the eight arsenic species were in the range 0.03–0.23 μg L⁻¹ based on 3σ for the blank response (n=5). The precision was calculated to be 2.4–8.0% (RSD) for the eight species. The method was successfully applied to several marine samples, e.g. oysters, fish, shrimps, and marine algae. Low-power microwave digestion was employed for extraction of arsenic from seafood products; ultrasonic extraction was employed for the extraction of arsenic from seaweeds. Separation of arsenosugars was achieved on an anion-exchange column. Concentrations of arsenosugars 2, 3, and 4 in marine algae were in the range 0.18–9.59 μg g⁻¹. This paper was presented at the European Winter Conference 2005     

Photosynthese isomerer octacarbonyl-μ-η3:3-2,5-hexadien- 1,4-diyldimangan-komplexe

UV irradiation of decacarbonyldimanganese(0) and 1,3,5-hexatriene at 243 K yields two isomeric (EE, EZ) octacarbonyl-μ-η^3:3 -2,5-hexadiene-1,4-diyldimanganese complexes, which were characterized by C, H elemental analyses and by IR and ¹H NMR spectroscopy.     

Determination of 16 insect growth regulators in edible Chinese traditional herbs by liquid chromatography electrospray tandem mass spectrometry

A new sensitive multiresidue liquid chromatography–tandem mass spectrometry (LC-MS/MS) analytical method for the determination of 16 insect growth regulator (IGR) residues—RH-5849 (1,2-dibenzoyl-1-tert-butylhydrazine), halofenozide, methoxyfenozide, chromafenozide, fufenozide, tebufenozide, diflubenzuron, chlorbenzuron, triflumuron, hexaflumuron, novaluron, lufenuron, teflubenzuron, flucycloxuron, flufenoxuron, and chlorfluazuron—in herbs (Perilla frutescens, flos chrysanthemi, lily bulbs, and ginger) has been developed. After the herbs had been extracted with acetonitrile, a combined graphitized nonporous carbon/aminopropyl (ENVI-Carb/LC-NH₂) cartridge and a Florisil cartridge were used to clean up the extracts. LC-MS/MS was performed in multiple reaction monitoring mode with two specific precursor ion–product ion transitions per IGR to confirm and quantitate the residues in herbs. Quantitation was performed on the basis of matrix-matched calibrations. The method showed excellent linearity (r ² > 0.99) and precision (relative standard deviations of 13.6 or lower) for all the target insecticides. The limits of quantitation were 0.6-10 μg kg^-1 for the 16 insecticides in the four herbs. The average recoveries, measured at three concentrations (0.01, 0.1, 1 mg kg^-1), were in the range 74.8-105.3%. The method was satisfactorily applied for the analysis of 60 herb samples (Perilla frutescens, flos chrysanthemi, lily bulbs, and ginger). Hexaflumuron was detected at concentrations of 0.029 and 0.051 mg kg^-1 in Perilla frutescens.     

Supramolecular catalytic systems based on anionic amphiphiles and polyethyleneimine for hydrolytic cleavage of phosphorus ester bonds

Self-organization in individual and binary systems based on polyethyleneimine (PEI) and amphiphilic sulfonatocalix[4]resorcinarene was studied by conductometry, tensiometry, dynamic light scattering, and ¹H NMR spectroscopy. The critical concentrations of micelle formation and aggregate sizes were determined. The enhancement of the catalytic effect on the hydrolysis of O-ethyl O-p-nitrophenyl chloromethylphosphonate was shown in the following series of the systems: PEI-water < PEI—calixarene-water < PEI—calixarene—La^III—water. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 366–373, February, 2008.     

Thermochemistry of heteroatomic compounds

The enthalpies of solvation of four geometric isomers of 2,5-dimethyl-1-phenyl-1-thioxophosphorinan-4-one in chloroform, nitrobenzene, and methanol were calculated using the enthalpies of vaporization of the isomers determined by the modified Solomonov—Konovalov method from the enthalpies of solution of the compounds in CCl₄ andp-xylene and molar refractions. The enthalpies of formation (ΔH _f ^o) of the isomers in the condensed and gas phase were assessed in the framework of Benson's group additivity scheme by summing the ΔH _f ^o values for phosphacycloketone fragments obtained from molecular mechanics calculations with the contributions of the phenyl group and S atom attached to the P atom. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1533–1536, September, 2000.     

Enantioselective hydrogenation of levulinic acid esters in the presence of the Ru<Superscript>II</Superscript>-BINAP-HCl catalytic system

The rate of hydrogenation of γ-ketoesters MeCOCH₂CH₂COOR (R = Et, Prⁱ, Bu^t) in the presence of the chiral Ru^II—BINAP catalyst (BINAP is 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) greatly increases upon the addition of 5–10 equivalents of HCl with respect to ruthenium. In the hydrogenation of ethyl levulinate, the optically active γ-hydroxy ester initially formed would cyclize by ∼95% to give γ-valerolactone with optical purity of 98–99% ee. When the Ru(COD)(MA)₂—BINAP—HCl catalytic system is used (COD is 1,5-cyclooctadiene, MA is 2-methylallyl), complete conversion of the ketoester (R = Et) in EtOH is attained in 5 h at 60 °C under an H₂ pressure of 60–70 atm. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2301–2304, October, 2005.     

Thermal,physicochemical and microstructural studies of binary organic eutectic systems

Solid–liquid phase equilibrium data of three binary organic systems, namely, 3-hydroxybenzaldehyde (HB)—4-bromo-2-nitroanilne (BNA), benzoin (BN)—resorcinol (RC) and urea (U)—1,3-dinitrobenzene (DNB), were studied by the thaw–melt method. While the former two systems show the formation of simple eutectic, the third system shows the formation of a monotectic and a eutectic with a large immiscibility region where two immiscible liquid phases are in equilibrium with a liquid of single phase. Growth kinetics of the pure components, the monotectic and the eutectics, studied by measuring the rate of movement (v) of solid–liquid interface in a thin U-tube at different undercoolings (ΔT) suggests the applicability of the Hillig–Turnbull’s equation: v = u (ΔT) ⁿ , where v and n are the constants depending on the nature of the materials involved. The thermal properties of materials such as heat of mixing, entropy of fusion, roughness parameter, interfacial energy, and excess thermodynamic functions were computed from the enthalpy of fusion values, determined by differential scanning calorimeter (Mettler DSC-4000) system. The role of solid–liquid interfacial energy on morphologic change of monotectic growth has also been discussed. The microstructures of monotectic and eutectics were taken which showed lamellar and federal features.     

Fatty-acid composition and secondary metabolites from slightly polar extracts of the aerial part of <Emphasis Type="Italic">Primula macrocalyx</Emphasis>

Flavones 2′,5′-dimethoxyflavone, 3′-methoxy-4′,5′-methylenedioxyflavone, 3′,4′-dimethoxyflavone, 5,6,2′,3′,6′-pentamethoxyflavone, and 5,6,2′,3′,5′,6′-hexamethoxyflavone; salicylates, methyl-4-methoxysalicylate and peonol; and bisbibenzyl polyphenol riccardin C were isolated for the first time from the acetone extract of the aerial part of Primula macrocalyx Bge. The content of free and total fatty acids was determined by GC and GC—MS. Palmitic (16:0), octadecatetraenoic 18:4 (6,9,12,15), linoleic 18:2 (9,12), and α-linolenic 18:3 (9,12,15) were the principal acids from the aerial part of Primula macrocalyx. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 457–460, September-October, 2008.     

Calculation of the hydrogen binding energies of complexes between formamide and adenine-thymine pair

The hydrogen bonding of complexes formed between formamide and adenine-thymine base pair has been completely investigated in the present study. In order to gain deeper insight into structure, charge distribution, and energies of complexes, we have investigated them using density functional theory at 6–311++G(d, p), 6–31G, 6–31+G(d), and 6–31++G(d, p) level. Seven stable cyclic structures (ATF1–ATF7) being involved in the interaction has been found on the potential energy surface. In addition, for further correction of interaction energies between adenine—thymine and formamide, the basis set superposition error associated with the hydrogen bond energy has been computed via the counterpoise method using the individual bases as fragments. The infrared spectrum frequencies, IR intensities and the vibrational frequency shifts are reported.     

Synthesis of optically active omeprazole by catalysis with vanadyl complexes with chiral Schiff bases

A new method for the preparation of optically active omeprazole, consisting in asymmetric oxidation of the corresponding sulfide with the use of vanadyl complexes with chiral Schiff bases as the catalysts has been elaborated. The best results of the oxidation were achieved by the use of the combination VO(acac)₂—2-[{(1S,2S,3R,5S)-3-hydroxymethyl-2,6,6-trimethyl-bicyclo[3.1.1]hept-2-ylimino}methyl]phenol—N-ethyl-N,N-diisopropylamine. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1648–1653, August, 2008.     

The role of protic solvent in asymmetric hydrogenation of methyl levulinate in the presence of a ruthenium-containing catalyst

A comparative study of asymmetric hydrogenation and deuteration of methyl levulinate catalyzed by the Ru^II—(S)-BINAP—HCl system (BINAP is 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) in MeOH and MeOD was carried out. The results obtained suggest an important role of the protic solvent in the formation of catalytically active ruthenium complexes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 531–533, March, 2007.