Development of TfOH-Catalyzed Spirocyclization by Intramolecular Friedel-Crafts-type 1,4-Addition: Application to the Total Synthesis of the Unusual Proaporphine Alkaloid (±)-Misrametine

An effective method was developed for TfOH-catalyzed construction of spiroindanes and spirotetralines containing an all-carbon quaternary stereocenter. Intramolecular Friedel-Crafts-type 1,4-addition of the substrates which were di- or trimethoxybenzene and 2-cyclohexenone linked by an alkyl chain proceeded smoothly in the presence of 30 mol % of TfOH. A variety of spiroindanes and spirotetralines were obtained with moderate to excellent yield by this method. The reaction was successfully applied in the first total synthesis of the unusual proaporphine alkaloid (±)-misrametine, which included the gram-scale spirocyclization and selective O-demethylation used KCN in DMSO condition as key steps.     

Skewered reactions in free‐radical crosslinking (co)polymerizations of liquid polybutadiene as internal olefinic multivinyl crosslinker

As an extension of our continuing studies concerned with the mechanistic discussion of network formation in the free‐radical crosslinking (co)polymerization of multivinyl monomers, this work refers to the skewered reactions in the crosslinking (co)polymerizations of liquid polybutadiene rubber (LBR) as an internal olefinic multivinyl monomer or crosslinker, especially focused on the competitive occurrence of both addition or skewered reaction to internal carbon–carbon (CC) double bonds and abstraction reaction of allylic hydrogens in LBR by growing polymer radical. Thus, LBR is regarded as an internal olefinic multiallyl monomer‐linked allyl groups (? CH?CH? CH₂? ) with methylene units (? CH₂? ). First, gelation in the polymerization of LBR was explored in detail, especially at elevated temperatures. The occurrence of intermolecular crosslinking was easier in the order LBR > LBR containing 20 mol % of 1,2‐structural units > liquid polyisoprene rubber. Then, we pursued the polymerization of LBR using dicumyl peroxide (DCPO) as typical organic peroxide used at elevated temperatures. The primary cumyloxy radical generated by the thermal decomposition of DCPO may add to CC double bond or abstract allylic hydrogen or undergo β‐scission to generate a secondary methyl radical. The initiation by the cumyloxy radical was omitted. The ratio of allylic hydrogen abstraction to β‐scission reaction was estimated; thus, only 39% of cumyloxy radical was used for the allylic hydrogen abstraction reaction. The addition of methyl radical to CC double bond was clearly observed. Finally, we pursued the intermolecular and intramolecular skewered reactions in free‐radical crosslinking LBR/vinyl pivalate copolymerizations. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Crystal Structure of Regularly Th‐Symmetric [U(NO3)6]2− Salts with Hydrogen Bond Polymers of Diamide Building Blocks

Hexanitratouranate(IV), [U(NO₃)₆]^2?, has been crystallized with anhydrous H⁺‐involving hydrogen bond polymers connected by selected diamide building blocks. Thanks to the significant moderation of electrostatic interactions between the anions and cations, the molecular structure of [U(NO₃)₆]^2? in these compounds is regularly T_h‐symmetric. The f–f transitions stemming from 5f² configuration of U⁴⁺ are strictly forbidden by the Laporte selection rule in such a centrosymmetric system, so that the obtained compounds are nearly colourless in contrast to other U^IV species usually coloured in green.     

Evaluation of electrodeposited gold nanostructures for applications in QCM sensing

The electrodeposition of gold nanostructures increases the surface area of a biosensor, which brings an enhancement of the sensitivity by increasing the amount of analyte binding to the surface. To evaluate the relationship among the surface structure, the area and the analyte binding, we quantitatively analyzed them for quartz crystal microbalance (QCM) sensing by scanning electron microscopy and cyclic voltammetry measurements. The results indicate a several-times increase of analyte bindings, and also the limitation of the sensing performance.     

Culcitiolides A-D, four new eremophilane-type sesquiterpene derivatives from Senecio culcitioides

Four new eremophilane-type sesquiterpenes, culcitiolides A-D, were isolated from the stem of Senecio culcitioides Sch. Bip (Asteraceae). Their structures were established by detailed 2D NMR spectroscopic and single-crystal X-ray experiments. These compounds were assessed for inhibitory activity against nuclear factor kappaB (NF-kappaB). Culcitiolides C and D at 20 microM showed 97 and 100% inhibition of NF-kappaB activity, respectively.     

The effect of mass transfer on the temperature gradient of a crystal growing from melt

The change in the temperature gradient on the crystal side while the rate of crystal growth from melt is varied has long been debated. Abe and Takahashi have recently reported an unambiguous experimental demonstration that the temperature gradient is a decreasing function of the growth rate, which is different from previous theories, experimental results, and widely held notion of other researchers. The present paper provides a theoretical basis for this seemingly peculiar effect of the growth rate on the temperature gradient. The essential matter is the effect of mass transfer, the role of which had been commonly disregarded in old studies. Although the rate of mass transfer is not large compared to that of heat conduction, it is proven that the temperature gradient is subjected to the mass transfer in a definite manner. Our analysis shows that the effect becomes significant when the crystal diameter is large, which is consistent with the experimental observation. Another effect of the mass transfer is the change in the shape of melt/crystal interface. In old studies, the temperature gradient was determined by Stefan's equation; however, this treatment confuses the cause and effect. The temperature gradient should be determined by the fundamental equation of heat conduction. When the gradient is determined in this way, the shape of the melt/crystal interface spontaneously adjusts to satisfy Stefan's equation.     

Formation,growth and ageing of clathrate hydrate crystals in a porous medium

An experimental study was performed to visually observe the driving force dependence of hydrate growth in a porous medium filled with either liquid water and dissolved CO₂ or liquid water and gaseous CO₂. The given system subcooling, ΔT _sub, i.e. the deficiency of the system temperature from the triple CO₂?hydrate?water equilibrium temperature under a given pressure, ranged from 1.7?K to 7.3?K. The fine dendrites initially formed at ΔT _sub?=?7.3?K changed quickly into particulate crystals. For ΔT _sub?=?1.7?K, faceted hydrate crystals grew and the subsequent morphological change was hardly identified for an eight-day observation period. These results indicate that the physical bonding between hydrate crystals and skeletal materials becomes stronger with decreasing driving force, suggesting that the fluid dynamic and mechanical properties of hydrate-bearing sediments vary depending on the hydrate crystal growth process.     

Vanadium isotopic composition of the sea squirt (Ciona savignyi)

Vanadium (V) in the sea squirt (Ciona savignyi) from Onagawa Bay, Miyagi, Japan, was isolated and purified through adsorption on a diamine resin and anion and cation exchanges after the dissolution of sea squirt samples with nitric acid and hydrogen peroxide. The (50)V/(51)V isotope ratio of V thus obtained was mass-spectrometrically determined to be from 2.51×10(-3) to 2.55×10(-3) with the average of 2.53×10(-3) by the thermal ionisation technique. This value agreed with those of vanadyl chloride and vanadyl nitrate both prepared from vanadyl sulphate (Wako Pure Chemical Industries, Ltd., Japan) and of V in coastal seawater (Shimokita Peninsula, Aomori, Japan) within experimental uncertainties (standard deviation of±0.04), which suggested that no appreciable V isotope fractionation occurs accompanying V uptake by the sea squirt from sea water.