Boc-protected 1-(3-oxocycloalkyl)ureas via a one-step Curtius rearrangement: mechanism and scope

1-(3-Oxocyclobutyl) carboxylic acid (4a) was converted into N-Boc-protected 1-(3-oxocyclobutyl) urea (5a), a key intermediate for the preparation of agonists of metabotropic glutamate receptor 5, in one-step when treated with diphenyl phosphoryl azide and triethylamine in tert-butanol. The mechanism of the reaction involves a nucleophilic addition of the in situ generated tert-butyl carbamate to the isocyanate intermediate. This reaction is applicable to other 1-(3-oxocycloalkyl) carboxylic acids but not to linear γ-keto carboxylic acids.     

Phosphonium salt induced stereoselective allylic rearrangement during chlorination of α-hydroxyallylphosphinates

α-Hydroxyallylphosphinates were stereoselectively converted to γ-chloro allylphosphinates when treated with Ph₃P and CCl₄, via substitution of hydroxyl and migration of double bond. The reaction was promoted by phosphonium cation that acted as Lewis acid.     

Electrophile-driven copper-catalyzed one-pot synthesis of 3-halogen quinoline derivatives

A convenient and regioselective one-pot synthesis of 3-chloride or 3-bromide quinoline derivatives was achieved through a Grignard addition reaction by alkynyl Grignard regent to o-trifluoroacetyl aniline and a Cu(II)-catalyzed cyclization–halogenation tandem reaction with aqueous HCl or HBr as electrophilic reagent.     

Theoretical study on the gas phase reaction of propargyl alcohol with hydroxyl radical

The reaction of propargyl alcohol with hydroxyl radical has been studied extensively at CCSD(T)/aug‐cc‐pVTZ//MP2/cc‐pVTZ level. This is the first time to gain a conclusive insight into the reaction mechanism and kinetics for this important reaction in detail. Two reaction mechanisms were revealed, namely addition/elimination and hydrogen abstraction mechanism. The reaction mechanism confirms that OH addition to C?C triple bond forms the chemically activated adducts, IM1 (·CHCOHCH₂OH) and IM2 (CHOH·CCH₂OH), and the hydrogen abstraction pathways (? CH₂OH bonded to the carbon atom and alcohol hydrogen) may occur via low barriers. Harmonic model of Rice–Ramsperger–Kassel–Marcus theory and variational transition state theory are used to calculate the overall and individual rate constants over a wide range of temperatures and pressures. The calculated rate constants are in good agreement with the experimental data. At atmospheric pressure with Ar as bath gas, IM1 (·CHCOHCH₂OH) and IM2 (CHOH·CCH₂OH) formed by collisional stabilization are dominant in the low temperature range. The production of CHCCHOH + H₂O via hydrogen abstraction becomes dominate at higher temperature. The fraction of IM3 (CH₂COHCH₂·O) is very significant over the moderate temperature range. © 2014 Wiley Periodicals, Inc.     

Cd2+ Counterion-Assisted Synthesis of Uniform CdS Nanospheres Capped with the Anionic Surfactant Sodium dodecylsulfate

Uniform cadmium sulfide (CdS) nanospheres were successfully prepared in the presence of the anionic surfactant sodium dodecylsulfate (SDS) at an appropriate concentration and relatively low temperature. Zeta potential data were collected for the three kinds of CdS particles to verify the existence of the Cd²⁺counterion on the CdS surface and Charge reversal; this was crucial for the explanation of how the anionic SDS surfactant molecules adsorbed on the negatively charged surface. Moreover, we confirmed that SDS had coated the surface of CdS nanospheres using infrared spectroscopy, and thermogravimetric analysis. An counterion assisted mechanism accounting for synthesis of CdS nanospheres could be widely used in the synthesis of nanomaterials if there is specific adsorption of the counterion. The CdS nanospheres showed good performance for the rapid adsorption of methylene blue.     

Salinity Selection for a Low Salinity Water-Low Salinity Surfactant Process

A laboratory selection of salinity for a low salinity water-low salinity surfactant (LS-LSS) process is presented in this paper with systematical investigation on surfactant phase behavior, interfacial tension (IFT), and dynamic retention in porous media with IOS2024 and isoamyl alcohol (IAA) as surfactant system. The results show that 0.4 wt% IOS2024 with 1 wt% IAA can provide ultra-low IFT of 10^?3 mN/m at around 3000–4000 mg/L total dissolved solids, but at that salinity range the surfactant retention is very high. The search for an optimum surfactant formulation has to consider solution properties and retention in addition to the low IFT. The salinity for a LS-LSS process should thus not be focused on either optimal salinity or ultra-low IFT, but instead the best choice could be a compromise between the properties in question. The three-phase region, where ultra-low IFT are found, is also associated with high retention values. However, we show that as salinity is increased from a two-phase region with oil solubilized in a water continuous microemulsion, there is a region close to the three-phase boundary which has potential. This region does not give ultra-low, but fairly low (10^?2 mN/m in this case) interfacial tensions, and also significantly lower retention.      

A green strategy for lithium isotopes separation by using mesoporous silica materials doped with ionic liquids and benzo-15-crown-5

Three new mesoporous silica materials IL15SGs (HF15SG, TF15SG and DF15SG) doped with benzo-15-crown-5 and imidazolium based ionic liquids (C₈mim⁺PF₆ ^?, C₈mim⁺BF₄ ^? or C₈mim⁺NTf ₂ ^? ) have been prepared by a simple approach to separating lithium isotopes. The formed mesoporous structures of silica gels have been confirmed by transmission electron microscopy image and N₂ gas adsorption–desorption isotherm. Imidazolium ionic liquids acted as templates to prepare mesoporous materials, additives to stabilize extractant within silica gel, and synergetic agents to separate the lithium isotopes. Factors such as lithium salt concentration, initial pH, counter anion of lithium salt, extraction time, and temperature on the lithium isotopes separation were examined. Under optimized conditions, the extraction efficiency of HF15SG, TF15SG and DF15SG were found to be 11.43, 10.59 and 13.07 %, respectively. The heavier isotope ⁷Li was concentrated in the solution phase while the lighter isotope ⁶Li was enriched in the gel phase. The solid–liquid extraction maximum single-stage isotopes separation factor of ⁶Li–⁷Li in the solid–liquid extraction was up to 1.046 ± 0.002. X-ray crystal structure analysis indicated that the lithium salt was extracted into the solid phase with crown ether forming [(Li_0.5)₂(B15)₂(H₂O)]⁺ complexes. IL15SGs were also easily regenerated by stripping with 20 mmol L^?1 HCl and reused in the consecutive removal of lithium ion in five cycles.     

Characterization of radioactive cobalt on graphene oxide by macroscopic and spectroscopic techniques

Graphene oxide (GO) was synthesized using the modified Hummers method and characterized by XRD and FTIR. The sorption of ⁶⁰Co(II) on GO as a function of contact time, pH, polyacrylic acid, ionic strength, temperature and solution concentration was studied by batch technique. The sorption kinetics indicated that the sorption of ⁶⁰Co(II) on GO could be simulated by the pseudo-second-order model very well. The maximum sorption capacities of GO for ⁶⁰Co(II) calculated from Langmuir model at pH 6.40 and T = 300 K was ~62.0 mg/g. The thermodynamic parameters from the temperature-dependent sorption isotherms indicated that the ⁶⁰Co(II) sorption on GO was an endothermic and spontaneous process. The interaction mechanism between GO and Co(II) were outer-sphere surface complexation or ion exchange at pH <7, whereas the inner-sphere surface complexation was observed at pH 7–9 in terms of the analysis of XPS spectra.     

Simultaneous determination of nine lignans from Schisandra chinensis extract using ultra‐performance liquid chromatography with tandem mass spectrometry in rat plasma,urine, and gastrointestinal tract samples: Application to the pharmacokinetic study of Schisandra chinensis

The fruit of Schisandra chinensis is a well‐known herbal medicine and dietary supplement due to a variety of biological activities including antihepatotoxic and antihyperlipidemic activities. However, the simultaneous validation methodology and pharmacokinetic investigation of nine lignans of S. chinensis extract in biological samples have not been proved yet. Thus, the present study was undertaken to develop the proper sample preparation method and simultaneous analytical method of schisandrol A, gomisin J, schisandrol B, tigloylgomisin H, angeloylgomisin H, schisandrin A, schisandrin B, gomisin N, and schisandrin C in the hexane‐soluble extract of S. chinensis to apply for the pharmacokinetic study in rats. All intra‐ and interprecisions of nine lignans were below 13.7% and accuracies were 85.1–115% and it is enough to evaluate the pharmacokinetic parameters after both intravenous and oral administration of hexane‐soluble extract of S. chinensis to rats.     

Identification and analysis of alkaloids in cortex Phellodendron amurense by high‐performance liquid chromatography with electrospray ionization mass spectrometry coupled with photodiode array detection

Alkaloids from Cortex Phellodendron amurense Rupr. were identified to determine the material basis for the bioactivity of this herb. HPLC–ESI‐MS with photodiode array detection coupled to XCharge C₁₈ column was applied to analyze the alkaloids qualitatively and quantitatively. A total of 37 alkaloids were identified and tentatively characterized from the ethanol extract by online ESI‐MSⁿ fragmentation and UV spectral analysis. A total of ten alkaloids, including four novel natural products, were tentatively identified for the first time in P. amurense. The fragmentation pathways for certain compounds were analyzed. The contents of a pair of isomers (columbamine and jatrorrhizine) and four main alkaloids (phellodendrine, magnoflorine, berberine, and palmatine) were simultaneously quantified using the aforementioned method. Results showed that the newly discovered and known components of P. amurense were helpful in determining the material basis for the bioactivity of the herb. The application of the XCharge C₁₈ column is a suitable and practical method for the isolation of alkaloids in plants.