Topomerization of substituted 1-amino- and 1-oxy-Δ2-1,2,3-triazolines

For 1-amino- and 1-oxy-²-1,2,3-triazolines, retardation (on the NMR time scale) is observed for rotation around the exocyclic N-N or N-O bond; the measured barriers to topomerization amount to 8.3–13.8 kcal/mole.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 790–794, April, 1991.     

A cascade thermal isomerisation of cyclobutane di-(carbomethoxy) Δ2-1,2,3-triazolines with intramolecular 1,3-dipolar cycloreversion as the key step

Unprecedented thermal isomerisation of the strained Δ²-1,2,3-triazolines led to the formation of products possessing a novel 1,2,7-triaza-[3.3.0]octa-2-ene ring system incorporated in a norbornane framework. Experimental evidence and quantum chemical calculations have been used to support a postulated reaction mechanism involving as the first step, a rare example of intramolecular 1,3-dipolar cycloreversion. Subsequently, several steps involving 1,3-dipolar ring closure, hydrogen shifts and an intramolecular addition are postulated leading to the observed product of this deep-seated isomerisation. The influence of changing substituents on the product outcome of this novel reaction cascade was also studied.     

Chemical characterisation of oxidative degradation products of Δ-THC

The chemical analysis of a sample of Δ⁹-THC, which had been stored in an ethanol/propylene glycol solution for 5 years, resulted in the isolation of several hydroxylated Δ⁹-THC derivatives, the main of which were trans-cannabitriol monoethyl ether (4) and trans-propanediol ethers 7 and 8. cis-Cannabitriol monoethyl ether (5) and the oxidised derivatives 3 and 6 were detected in lesser amounts. The structure elucidation of the unprecedented cannabinoids 3, 5, 7 and 8 was achieved mainly by NMR techniques. Full NMR assignment of compounds 4 and 6 were also made. The detection of cannabitriol (6) and the corresponding solvent-adduct analogues (compounds 4-8) was in agreement with the decomposition mechanisms previously proposed for Δ⁹-THC. The isolation of the endoperoxide 3 represents indirect evidence of the existence of unstable precursors that were suspected to be intermediates in the non-enzymatic oxidation pathway of Δ⁹-THC. Both isomers of cannabitriol monoethyl ether exhibited weak affinity at either CB₁ (K_i=2.25, 6.30 μM) or CB₂ cannabinoid receptors (K_i=1.97, 3.13 μM), the trans isomer always being more potent than the cis isomer.     

Preparation of β-caryophyllene oxidation products and their determination in ambient aerosol samples

Oxidation of β-caryophyllene with ozone followed by reduction was carried out in dichloromethane. Reaction led to the formation of β-caryophyllene aldehyde (11%, purity 90.8%) and β-nocaryophyllone aldehyde (79%, purity 99%). Compounds were purified and separated by liquid–liquid extraction and flash chromatography. Identifications were achieved by electron-impact and electrospray ionization mass spectrometry, and precise structures were confirmed by one and two-dimensional nuclear magnetic resonance spectroscopy. The prepared compounds were used in the analysis of ambient aerosol samples collected during spring 2003 at Hyytiälä, Finland. β-Nocaryophyllone aldehyde was positively identified and quantified in ambient aerosol samples for the first time. The amount of quantified β-nocaryophyllone aldehyde of aerosol origin was 17.4?±?1.0 ng m^?3 of sampled air. Comparison with previous findings led to the conclusion that oxidation products of β-caryophyllene participate in biogenic aerosol formation over boreal forest during late spring.     

μ-Acyl Os3 clusters containing metallocenyl substituents and products of their protonation

Previously unknown μ-acyl osmium clusters containing simultaneously permethyl-metallocenyl and Os₃ cluster fragments were synthesized. The IR, UV, NMR (¹H and¹³C), and FAB-MS spectra were examined. Protonation of the clusters proceeds at the metal atom of the metallocenyl fragment. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 180–183, January, 1999.     

The fast and the slow: folding and trapping of λ6-85

Molecular dynamics simulations combining many microsecond trajectories have recently predicted that a very fast folding protein like lambda repressor fragment λ(6-85) D14A could have a slow millisecond kinetic phase. We investigated this possibility by detecting temperature-jump relaxation to 5 ms. While λ(6-85) D14A has no significant slow phase, two even more stable mutants do. A slow phase of λ(6-85) D14A does appear in mild denaturant. The experimental data and computational modeling together suggest the following hypothesis: λ(6-85) takes only microseconds to reach its native state from an extensively unfolded state, while the latter takes milliseconds to reach compact β-rich traps. λ(6-85) is not only thermodynamically but also kinetically protected from reaching such "intramolecular amyloids" while folding.     

Highly Substituted Δ3-1,2,3-Triazolines: Solid-State Emitters with Electrofluorochromic Behavior

Highly substituted Δ³-1,2,3-triazolines can be prepared by reaction of triarylvinyl Grignard reagents with functionalized organic azides. The heterocycles are fluorescent in the solid state, and—depending on the substituents—they can display aggregation-induced emission. Upon oxidation, the triazolines form stable radical cations with altered photophysical properties. Therefore, they represent rare examples of solid-state emitters with intrinsic electrofluorochromic behavior.     

Microbial bioreductions of γ- and δ-ketoacids and their esters

A series of yeasts were used in the bioreductions of aliphatic and aromatic γ- and δ-ketoacids and esters to investigate the preparation of enantiomerically pure γ- and δ-lactones through the intermediacy of their corresponding γ- and δ-hydroxyacids and esters. Bioreduction of ethyl 4-oxononanoate 2a with Pichia etchellsii afforded the γ-nonanolide (+)-5a with 99% e.e., while Pichia minuta proved to be the best choice for the bioreduction of ethyl 2-oxocyclohexylacetate 2e, which afforded cis-(−)-5e and trans-(−)-5e with 98 and 99% e.e., respectively. Reduction of 3-(2-oxocyclohexyl)propionic acid 3e with Pichia glucozyma gave predominantly the corresponding δ-lactone trans-(−)-6e with 94% e.e., whose absolute configuration was determined by means of CD spectroscopy.     

Reactivity, 31P, 13C, 1H NMR and IR Studies of Δ5-3-Dimethylamino-3-Oxo-1,2,3- Diazaphospholines

Abstract

In precedent work research (1)(2) we have reported a new synthesis method of the Δ⁵-3- dimethylamino-3-oxo-l,2,3 diazaphospholine derivatives (D_i). In this present work, we have to detail the reactivity and the structure of those heterocycles by N.M.R. (³¹P, ¹³C, ¹H) and I.R. In Infra-Red spectroscopy, we show the existence of the intermolecular hydrogen bond of some compounds. The spectrum(³¹P, ¹³C, ¹H) and I.R. was reported of (D_i).     

The Raman spectra of the benzene—chlorine and benzene—bromine charge-transfer complexes

The Raman spectra of the “charge-transfer” complexes of benzene with chlorine and bromine in solutions have been recorded. The low-temperature Raman spectra of the crystalline compounds were also studied. The structure of the complexes and the interaction between the components have been discussed.     

Optical and electrochemical properties of novel fused tricyclic thiophene–15-crown-5 systems and their complexes with Mg and Ba ions

New polycyclic aromatic derivatives annulated both with thiophene and with 15-crown-5 ether moieties, crown naphthothiophenes, were synthesized via the Mallory photocyclization with the use of iodine as the mild oxidizer, while two isomeric products were readily separated by column chromatography. Their complexation with Ba²⁺ and Mg²⁺ cations was examined by both optical and electrochemical methods. Spectroelectrochemical studies indicate that the obtained compounds, depending on their structure, can be chemically stable in the oxidized state     

Chromophores with quinoxaline core in π-bridge and aniline or carbazole donor moiety: synthesis and comparison of their linear and nonlinear optical properties

Russian Chemical Bulletin - Two new D—π—A chromophores with the tricyanofuranyl acceptor (A), an amphi-divinyl quinoxaline π-electron conjugated bridge, and the carbazole or...     

Study of complex formation between ��-cyclodextrin and benzene

In this work study of complex formation of ??-cyclodextrin with benzene was performed both experimentally and theoretically. Interaction of benzene with ??-cyclodextrin in aqueous solutions was investigated by means of UV spectroscopy at temperatures in the range 291?C303 K. The stoichiometric composition, stability constant, and thermodynamic parameters of ????-cyclodextrin-benzene?? supramolecular structures formation were calculated from spectroscopic data. It was proved that 1:1 inclusion complex is mainly formed in aqueous solutions. The calculations of a spatial structure, formation energy, and vibration spectra in IR range for the complex of ??-cyclodextrin with benzene were performed by Hartree?CFock?CRoothaan method within PM3 semiempirical approximation with quantum chemistry package GAMESS (version 6.4). The calculated energy parameters for ????-cyclodextrin-benzene?? inclusion complex are in agreement with experimental data.     

Synthesis and characterization of new metal-free and metallophthalocyanines fused α-methylferrocenylmethoxy units

Synthesis of metal-free and metallophthalocyanines bearing α-methylferrocenylmethoxy units was described. Precursor 3 required for the preparation of phthalocyanines 4–9, was synthsized by the nucleophilic aromatic substitution reaction between α-methylferrocenylmethanol and 4-nitrophthalonitrile in dry DMF. The metal-free phthalocyanine 4 was prepared from 4-(α-methylferrocenylmethoxy)phthalonitrile 3 in 1-pentanol with a catalytic amount of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). Metallophthalocyanines (M = Zn, Cu, Co, Ni and Pb) were prepared by cyclotetramerization reaction of phthalonitrile with appropriate materials. The phthalonitrile, metal-free and metallophthalocyanines were characterized by ¹H and ¹³C NMR, FT-IR UV–Vis and mass spectral data, as well as elemental analyses, which were consistent with the proposed structures.     

Synthesis, structure and conformation of 1,3-difluorotetraphenyl benzene

The compound trifluoroiodomethane can be activated to react with the electron donor,1,4-dilithiotetraphenyl butadiene,by means of electron transfer catalysis (ETC).The structure of the product,1,3-difluorotetraphenyl,benzene (1),was determined by MS,NMR,and X-ray single crystal diffraction.The conformations of compound 1 and its derivatives were analysized by molecular mechanics.     

Determination of antifouling pesticides and their degradation products in marine sediments by means of ultrasonic extraction and HPLC–APCI–MS

A method has been developed for the simultaneous determination of antifouling pesticides and some of their degradation products, e.g. dichlofluanid, diuron, demethyldiuron, 1-(3,4-dichlorophenyl)urea, sea-nine, Irgarol 1051 and one of its metabolites (2-methylthio-4-tert-butylamino-s-triazine) in marine sediments. The determination of these compounds in sediment samples was performed by means of methanolic ultrasonic extraction then clean-up on an Isolute ENV+ solid phase extraction (SPE) cartridge. The resulting extract was then analyzed by reversed-phase high-performance liquid chromatography coupled with atmospheric-pressure chemical-ionization mass spectrometry in negative and positive ion modes (HPLC–APCI–MS). Recovery ranged from 54–109% for the antifouling agents and their degradation products. The determination limits for the different compounds varied between 0.2 and 1.6 μg kg^–1 dry sediment. The analytical procedure was successfully applied to the determination of these pesticides and their degradation products in marine sediment samples from different marinas of the Catalan coast. The compounds detected were: diuron, dichlofluanid, demethyldiuron, sea-nine, and Irgarol 1051. The highest concentrations were those of diuron and Irgarol 1051 – 136 and 88 μg kg^–1, respectively.     

Co-isolation of deoxynivalenol and zearalenone with sol–gel immunoaffinity columns for their determination in wheat and wheat products

The paper describes a sample clean-up method for the co-isolation of deoxynivalenol (DON) and zearalenone (ZON), two mycotoxins naturally co-occurring in wheat. The method is based on immunoaffinity columns prepared by co-immobilising anti-DON and anti-ZON antibodies in a porous sol–gel glass. The main task in developing the method consisted in finding a loading medium allowing retention of both analytes as well as a common elution medium for the dissociation of both antigen–antibody complexes formed. This can be achieved by co-extracting DON and ZON with ACN–water (60:40, v/v), reducing the acetonitril concentration to 2.5% before loading an aliquot of the diluted sample extract onto the DON/ZON column. The columns are washed with 5 ml of MeOH–water (10:90, v/v) before DON and ZON are co-eluted with 4 ml of ACN–water (50:50, v/v). Concentrations of DON and ZON are determined with HPLC-UV and HPLC-fluorescence detection, respectively. The sample clean-up method was shown to be applicable to wheat and wheat products, e.g., cornflakes, milk wheat mash and rusk. Spiking experiments (spike level 500 μg DON/kg and 50 μg ZON/kg) resulted in recovery rates from 82% to 111%.     

Synthesis of 1,2,4-triazolines: base-catalyzed hydrazination/cyclization cascade of α-isocyano esters and amides

A convenient, efficient synthesis of 1,2,4-triazolines from α-isocyano esters/amides and azodicarboxylates is presented. The developed reaction cascade is based on a base-catalyzed hydrazination-type reaction followed by a subsequent cyclization providing the triazolines in good to excellent yields (75-99%). Phosphine-catalyzed and preliminary asymmetric phase-transfer catalysis approaches have also been investigated.     

Stereocontrolled self-assembly of luminescent lanthanide helicates and their enantiodifferentiation using Δ-TRISPHAT as the NMR resolving agent

Self-assembled supramolecular lanthanide constructs have great potential in luminescent bioprobes/sensors. Stereoselectivity on the lanthanide assemblies is needed to facilitate chiroptical probes and sensors. Herein we report the stereocontrolled synthesis of M₂L₃-type (M = metal ion, L = organic ligand) lanthanide triple-helicates using a chiral-induction strategy, where the periphery point-chirality [(R,R) or (S,S)] of the organic ligands was transferred into the metal centered chirality (ΔΔ or ΛΛ), thus leading to the formation of topological chiral (P or M) helicates. Moreover, commercially available Δ-TRISPHAT proved to be an effective NMR chiral resolving agent to differentiate between the two enantiomers of the helicate.     

Reactions of Au+ and Au− with benzene and fluorine-substituted benzenes

Reactions of gold anions and cations generated by laser desorption/ionization were studied in the FTICR spectrometer. Au⁻ associated with C₆F₆ to give the novel Au⁻(C₆F₆) complex, whose binding energy was estimated to be 24 ± 4 kcal mol⁻¹ from analysis of the radiative association (RA) kinetics. Au⁺ associated with C₆F₅H to give Au⁺(C₆F₅H), with binding energy estimated to be 31 kcal mol⁻¹. Au⁺ reacted with C₆H₆ to form the well known Au⁺(C₆H₆) and Au⁺(C₆H₆)₂ complexes. The observation of rapid charge transfer from Au⁺(C₆H₆) to C₆H₆ was interpreted as showing that benzene binds more strongly to neutral Au than to Au⁺. The neutral Au–C₆H₆ bond is accordingly concluded to be stronger than about 70 kcal mol⁻¹.